The following is an adaptation of what I wrote elsewhere already, here:
I thought Rabbi Riskin's talk was very good.
I'm reminded of Rabbi Eliyahu Benamozegh, a great 19th-century Italian rabbi, who said that the Gospels are second only to the Midrash, and that the difference between Qabala and the Trinity is ten minus three. (See the article by Alick Isaacs, cited here).
I'm also reminded of Rabbi Yaakov Emden, who believed the Christian Bible actually intends for Judaism to keep mitzvot and for gentiles to keep the Noahide laws. He believes the Christian Bible never intended Christianity to replace Judaism. (See here.)
The greatest problem with Christianity, then, would be that it turned the Mashiah (Messiah) into a demi-god, and believed that a man could be G-d. This is the central problem with Christianity, but it isn't clear that Jesus himself subscribed to this problematic concept. Jesus himself could be seen as a normative Pharisee not unlike Bar Kokhba or the like. (Not that Jesus couldn't also be viewed as a heretic. I'm offering a reconciliatory revisionist view.)
And so the only problem I see with Rabbi Riskin's talk is that while he distinguished between the first and second comings, he said nothing about the Mashiah being a G-d or not. This is iqar haseir min ha-sefer ("the principal subject matter is missing from the book").
When Rabbi Benamozegh expressed his great respect for Christianity as a religion and non-Jews as people, he was in no way influenced by censors. His remarks were written as parts of entire books he wrote about Judaism and Christianity (such as his Israel and Humanity). He also had a private correspondence with a Catholic who wanted to convert to Judaism, but who was convinced by Rabbi Benamozegh to become a Noahide instead. These weren't individual remarks by him. These were rather very systematic and comprehensive ideologies of his.
By the way, he also wrote an entire book criticizing Christianity, saying that its focus on spirituality and belief was inferior to Judaism's practical and this-worldly approach. So Rabbi Benamozegh wasn't afraid of criticizing Christianity. Also, he did convince this aforementioned Catholic to stop being Catholic anymore.
So I think Rabbi Benamozegh's view was basically one similar to Rabbis Riskin and Emden, viz. that:
(1) Christians are not idolaters. Their theology and metaphysics are troubling, but we need not accept Rambam that wrong beliefs lead to damnation. Meiri focuses on deed, not creed, saying that G-d is concerned with whether you are "bound by the ways of religion", viewing monotheism primarily as a way of life rather than a belief system. (Not that beliefs are unimportant, G-d forbid! But they are secondary. As Rabbi Dr. Isidore Epstein puts it, the Prophets criticized the pagans not for incorrect belief, but rather, because they sacrificed humans and oppressed the poor.) We can follow Meiri rather than Rambam. Even when others accept Rambam that belief is important, they emphasize that, contra Rambam, only deliberate heresy (b'meizid) is real heresy, whereas Rambam said even unintentional heresy (b'shogeg) is heresy. A Christian would be an unintentional heretic, because he really truly does wish to get close to G-d, even if he is confused.
Now, there remains the issue of whether Christians are idolaters. I honestly believe they are not, that they believe in the same G-d as Jews. According to Rabbi Dr. Eugene Korn, discussing Rabbi Soloveitchik's essay on interfaith dialogue, "Confrontation" (see here),
Maimonides is well known to have ruled that Christian trinitarianism is beyond the pale of legitimate theology, but given R. Soloveitchik’s statements about positive relations with Christians and his appearances at Christian institutions, it is likely that he agreed with other rabbinic authorities who reject Maimonides’ position.But this discussion is beside the point. If we were discussing a Jew entering a church, or his using Christian ritual objects, or other questions of avodah zara, then we'd have to clarify whether Christianity is idolatry or not. But right now, we are discussing our interpersonal human relationships with Christians, whether we can talk to them and tolerate them respectfully and lovingly. Whether or not they are technically idolaters, we can still follow the Meiri and say that since they are righteous and decent upstanding people who truly wish to come close to G-d, therefore, we may have good relations with them.
In Rabbi Dr. J. H. Hertz's Early and Late (Soncino Press, 1943), we read, (“A Vindication of Religion”, p. 197),
An essential element in that [religious] vision is God's holiness. And the Holy God can only be sanctified [i.e. made holy] through righteousness, Isaiah has for all time declared. That is, moral conduct is the beginning and end of religion, and men and nations are to be judged purely by their moral life. 'The righteous of all nations are heirs of immorality', is an unchallenged dogma of the Synagogue. In this way, undeviating insistence on absolute monotheism goes hand in hand with the broadest universalism. No wonder that the first voice raised in Western Europe for religious toleration was a Jewish voice. It was 900 years ago that the Spanish-Jewish philosopher and religious poet, Solomon ibn Gabirol, gave utterance, in a hymn that is still recited on the Day of Atonement in the older synagogues, to the then novel and daring conception, that every religion represents a longing for the Divine. He says,And Rabbi Hertz to Devarim 4:19 (Hertz Pentateuch p. 103) and in "Religious Tolerance" (Affirmations of Judaism; Sermons Addresses and Studies) quotes Malachi 1:11:'Thou art the Lord, and all beings are Thy Servants, Thy Domain:
And through those who serve idols vain
Thine honour is not detracted from,
For they all aim to Thee to come.'
For from the rising of the sun even unto the going down of the same My name is great among the nations, and in every place offerings are presented unto My name, even pure libations; for My name is great among the nations, saith the Lord of Hosts.Rabbi Hertz comments,
Even the heathen nations that worship the heavenly hosts pay tribute to a Supreme Being, and in this way honour My name; and the offerings which they thus present (indirectly) unto Me are animated by a pure spirit, God looking to the heart of the worshipper. This wonderful thought was further developed by the Rabbis, and is characteristic of the universalism of Judaism.
Rabbi Eugene Korn writes (One God: Many Faiths A Jewish Theology of Covenantal Pluralism),
Idolatry according to some rabbinic opinions (Rabbi Menachem Ha-Meiri, 13th century France, and those later rabbinic authorities who accepted his conceptualization of idolatry) is any ideology that rejects the above moral obligations, which are the foundations of any civil society. Importantly, there is no explicit requirement in the Noahide covenant to believe in God. The Noahide covenant is thus primarily moral, devoid of explicit theological doctrine. Even if it were to require belief in a generic creator who implanted a moral order into the cosmos and who ensures punishment for those violating that order (Meiri believed that one could not lead a coherent moral life without a belief in a Creator of heaven and earth who punished the guilty and rewarded the innocent. Like other pre-moderns, a secular ethic was untenable), at most Noahites would have to believe only that "God is" and that His moral authority is supreme—but no specific theology or a specific way to worship God.
There's a wonderful midrash by Abraham Lincoln, often quoted by rabbis who think Hazal said it. According to this midrash: idolater comes to Abraham, Abraham feeds him, asks him to make a blessing. The guy refuses to worship only one G-d (he cannot understand birkat ha-mazon's mention of only one G-d!), so Abraham throws him out. G-d says to Abraham: "I put up with this ignorant polytheist for seventy years, and you cannot live with him for an hour?".
See also Professor Marc Shapiro's article about Rabbi Jonathan Sacks's The Dignity of Difference, here.
(2) Rabbis Emden et. al. follow a revisionist view of Christianity, in which Jesus was a rabbi, perhaps an Essene or a messianic or an apocalyptic, but no worse than, say, a Habadnik. Paul twisted Christianity, not Jesus. So Jesus might have had some wrong beliefs, but he was still within the fold of legitimate Judaism, even if barely so. Therefore, Jesus's beliefs were Jewish, and the Gospels are like the Midrash (according to Rabbi Benamozegh). This doesn't mean we cannot disagree with Jesus and the Gospels, but it gives us common ground, and lets us criticize Paul's idolatrous pagan teachings and dismissal of the practical mitzvot, while, at the same time, acknowledging the Jewish truths that Christianity has. We can do this already (Rambam did it in the uncensored version of the Mishneh Torah, saying that Christianity and Islam paved the way for knowledge of G-d and Mashiah to permeate the world), but having this revisionist view of Jesus makes it easier. It gives us more common ground, and serves as a useful rhetorical tool.
Now, I am definitely concerned with Rabbi Riskin's statements, insofar as they are vague and incomplete. This is why I criticized him for failing to mention how the Jewish Mashiah is not G-d. I've often said that if Jesus comes back from the dead as Mashiah, then I'll accept him, but that I'll never ever accept him as anything but the Jewish Messiah, a very human one, charged not with vicariously atoning for our sins (which only G-d can do), but instead only with bring tiqun olam and knowledge of G-d. But my criticisms of Rabbi Riskin are against how he says what he says, and not what he says. Rabbi Riskin needs to be very careful about how he says what he says, lest he be misinterpreted. This is a very real concern, but as for the actual substance of what he says? - There, I completely agree with him, or at least, I'm close enough to his opinions to be living in the same neighborhood.
After all, I am not only a follower of Rabbi Meir Kahane. I'm also a follower of Rabbi Menahem ha-Meiri and Rabbi Eliyahu Benamozegh and Rabbi Haim David Halevi.