How disagreements used to happen: I think [idea]. Here's my evidence.

How they happen now: Speaking as a [member in X class], I believe [idea].

We've started to tie up our identities into our arguments, and when you do that you can't get around attacking who someone is as a person when they link their membership in a group to the epistemology of why they think something. This is my working theory for why people have started to equate speech with "literally violence". Disagreeing has become an attack on their identity, so it's only natural to interpret that in an extreme form.