If you call someone something (ie, racist, sexist, etc), and then recoil when you are “personally attacked” then you are an idiot, and I have no reservations about saying it.
Accusing someone of an -ism is a damned personal attack because you are attacking their very character. It’s no better than saying they are an idiot or a douche-bag.
So you don’t get to call someone names and then act offended if someone calls you names back.
There is a difference between name-calling (a perfectly acceptable shortcut to making a point, in my arrogant opinion), and wishing for bad things to happen (“I hope you die in a fire” — or, see many of the comments guys like Matt Forney get), and threatening someone (“I’m going to kill you in a fire.”).
And someone telling you that you’re an idiot for saying idiotic things is going to happen on the internet. Put on your big girl panties or go home.