Nothing in this headline says they werent up front about it.

Yeah, it's not good nor smart.

When does it justify physical violence?

If someone swaps my toast bread for buckwheat toast bread, I'm not going to start beating them up.

This is a minor deception, it can warrant at most being a bit mad at the person,and the fact that everyone seems to be okay with physical violence in such a case is pretty worrying.

And let's face it, the fact that it was about meat and a vegan is a big root of this, because people are so much into denial that they actually fantasize about beating up the people that remind them that it is immoral to eat meat.

And quick disclaimer, I am not vegan nor vegetarian, but I can simply admit that eating meat is immoral. For some reason people would rather defend more violence than to admit that.