Or so it seems to people in the 21st Century. I don't think that great thinkers are supposed to avoid intellectual errors. Or rather, it is compatible with greatness to get at last some things horribly wrong.
Of course, the Kantian position that most people roll their eyes on is his views on lying, particularly in his response to Benjamin Constant. There you get a sense that, yes, he's got that wrong, but there is something to be gained by coming to terms with him neverthteless.
HT: Ed Babinski.