The thing is, there are two different things meant by the word "extremism", and the word itself serves to conflate the two. One is what you discuss -- object-l

The thing is, there are two different things meant by the word "extremism", and the word itself serves to conflate the two. One is what you discuss -- object-level positions that are extreme in some way. This is, as you say, no vice. The other thing that is meant by "extremism" is what one might call "meta-level extremism"; it includes such things as trying to silence one's opponents rather than argue with them, the use of violence, etc. This, obviously, is a bad thing. (And while I called it "meta-level extremism" above, what it really is, I'd say, is illiberalism.) For this reason, I don't like the word "extremism", as it conflates the two. Of course, it's possible that the reason the same word is used for both is because, for pyschological reasons, in humans these tend to go together. But they are logically separate.