Everyone has different ethical frameworks. The label of "extreme" is arbitrary, not objective. I'm sure you would never rape or murder someone. Does that make you an extremist? You don't think it's OK to occasionally rape and murder people right? Vegans' ethical framework is that the murder of animals is unacceptable, and so there is no middle ground. That's not extremism, it's a different framework. To frame it as a spectrum is a misunderstanding.
Ah you said it much better than I did, I'll link your comment.