I think that it is important to remember that social progress is not accomplished only by accepting others for who they are, but also refusing to accept those who have acted to place themselves outside the society in unacceptable fashions, moving society away from where accepting them would bring it.
Yes, this position leaves room for a society to marginalize people. I'm okay with marginalizing murderers and having to talk through why we're accepting those of debatably acceptable beliefs. Moving society so that what is acceptable changes is fine... as long as it can also move away from things that are harmful.
Really. I don't see a reason to accept someone who would kill 80 kids. Marginalize away.