For the statists (such as O'Rouke), it seems that as long as you can find any opinion permitting government action, that action is alright. If Alexander Hamilton interpreted "general welfare" as a carte blanche, then who are we to disagree? The fact that others, such as Madison, disagreed with this interpretation of "general welfare", and the fact that the Federalists in general had succeeded in getting the Constitution ratified only assuaging the fears of the Antifederalists and convincing them that the federal government would have only limited, enumerated, delegated powers (which means "general welfare" cannot be a carte blanche), is seen as irrelevant by them.
Similarly, they'll cite Supreme Court decisions, as if a Supreme Court decision contradicting the Constitution is more valid than the Constitution itself. They'll say, "See, the Constitution permits X, because Judge So-and-so said so!" But the possibility that the judge was wrong, never occurs to them. The entire case law method of law is thus fundamentally moronic. What is authoritative is the Constitution, not anyone's personal opinion of it. Court decisions ought to be cited insofar as they are (thought) to express valid interpretations of the Constitution, not as having any authority in and of themselves.
The statists will cite actions of the Federalists like Adams and Hamilton, and say, "See, the Framers did it!" Now, I must admit, this IS a valid argument. When they make this argument, they are at least on reasonable territory. O'Rouke cites Adams's coerced insurance for sailors, and implies the rhetorical question, are we going to say that Adams, one of the Framers, did not know the Constitution? The argument is a seriously reasonable one. But there's still a problem: Madison's and Jefferson's Virginia and Kentucky Resolutions claimed, very vehemently, that Adams was eviscerating the Constitution. Regarding the "general welfare" clause, Madison's Virginia Resolution says,
That the General Assembly [of Virginia] doth also express its deep regret, that a spirit has in sundry instances, been manifested by the federal government, to enlarge its powers by forced constructions of the constitutional charter which defines them; and that implications have appeared of a design to expound certain general phrases (which having been copied from the very limited grant of power, in the former articles of confederation were the less liable to be misconstrued) so as to destroy the meaning and effect, of the particular enumeration which necessarily explains and limits the general phrases...So contra O'Rouke, yes, it is very possible that Adams did not understand the Constitution! Alternatively, I would say, the Framers themselves were more more correct than they knew, when they said men are sinful and liable to abuse power. In fact, when Jefferson was president, he imposed a trade embargo which New England thought unconstitutional, and the New Englanders quoted his own Kentucky Resolution right back at him in justifying their disobeying him. So I would say that it is far more significant when a Framer thought the Constitution forbade something, than when he thought the Constitution permitted it. כחא דהתרא עדיפא ("the power of permission is superior"), a permission is more novel (and thus more suspicious) than a prohibition. To forbid the government an exercise of power, is always the safest and most reasonable route, ספק דאורייתא לחומרא ("in a case of doubt about a Torah law, be strict"), in a case of doubt, we should be strict. To be lenient and permit the government an exercise of power, is suspicious and novel, and it is always possible that the official in power is either maliciously abusing his power, or else his own aspirations have clouded his judgement and he honestly believes his exercise of power is legitimate when it is in fact not. But when anyone interprets the Constitution as limiting the government's power (Madison: "I cannot undertake to lay my finger on that article of the Constitution which granted a right to Congress of expending, on objects of benevolence, the money of their constituents."), it is much more reasonable for us to take it at face value and as accurate and true.
These people will cherry-pick permissive legal opinions the same way that some lax and lazy Modern Orthodox Jews will, but with one difference: when a lax person cherry-picks an obscure leniency, he is affecting only himself, and if his cherry-picking is sinful, at least he is hurting only himself. But it is perverse to cherry-pick a lenient opinion for the government, because this means the government will use that leniency to exercise power over others. It is perverse to be lenient at someone else's expense.