"Respond intelligently, even to unintelligent treatment." (Lao-Tse)
People do dumb things to us. They say even dumber things. (Especially on social media.)
While it's easy to freak out and react in kind, it can also be easy to react by just ignoring it.
This may sound crazy, but every once in a while it's good to try and respond instead. Here are some examples:
Empathy: "Wow, it's obvious you really feel strongly about this."
Self-disclosure: "I don't think I've ever thought of it quite that way."
Curiosity: "So, what're you hoping I do in response to that statement?"
Challenge: "Is this something you'd like us to have a serious conversation about?"
Whether you try any of these responses should probably depend on the kind of relationship you have with the other person. And I certainly wouldn't recommend trying something like this every time you're treated or spoken to poorly.
But go ahead and put these into your tool belt, and try 'em out every once in a while. Just for practice.
(If it totally backfires, go ahead and blame me.)