Perhaps "nobody bats an eye" because the left has been doing this kind of thing for years, and in much worse ways. I'm not going to defend the use of insults by anyone, but will point out that people have been calling cops, "pigs" or saying "fry 'em like bacon" for years, and have even been calling Trump far worse things for a long time.
So if "nobody bats an eye", it's because the left has helped create this environment.