I was watching a movie where this guy’s wife was urging him to apologize to another guy he used to bully. His response was “people don’t just do that!” My friend agreed. I said “We’re people. We can do that right now.”
Me when some guy in a game voice chat goes off on a rant about how insane I am for expecting people online to have manners.
Having thick skin isn't mutually exclusive with telling people to do better when they're being dicks.
Ignoring rude behavior is the same as forgiving and allowing it.
(Edit: which is not to say everyone needs to dive into such a confrontation. First and foremost, protect yourself. The fact that vulnerable people who need to do so, exist, and that some of them can't, is the whole reason I don't just let cruel behavior pass.)