"Nastiness in the comments" and "people asking him to be more rigorous" aren't mutually exclusive. I heard a lot of this in person, so I can't easily provide references, but back when that was all going down I remember a lot of talk from Eliezer and other major contributors about how LW was getting unpleasantly nitpicky.

In Eliezer's case this probably has something to do with the fastest-gun-in-the-west dynamic, where if you're known as a public intellectual in some context you're going to attract a lot of people looking to gain some status by making you look stupid. But I heard similar sentiments from e.g. Louie, and he was never Internet famous like Eliezer was.