The right wingers love to do that too, not only the lefties. Call somebody "racist" or "socialist" and you have marked them as so bad that no further dialog is needed (or even possible).
I agree emphatically that this is on both sides. Those of us who have watched with relief and hope the decline of influence of irrational, moralizing, censoring fundamentalist Christians[1] (on the right) are somewhat shocked and disappointed to see such a dramatic uptick of irrational moralizing fundamentalist social justice activists[1] on the left.
[1] Not all of them! But enough to cause harm to society
