people automatically downvote anything critical of the Enlightenment

Evidence?

(It looks to me as if most of the unthinking downvoting on LW is done by neoreactionaries. But being not at all neoreactionary-minded myself, it's likely that it looks more that way to me than it is in reality.)

Of course, even if your claim were true that wouldn't suffice to make "crimethink" an appropriate word; the whole horror of the term in 1984 is that the Party tries (apparently quite successfully) to control not only actions, not only words, but thoughts, and did it by means a little more brutal than downvotes.