Leftists will always claim fringe cases while demanding that normalization of monstrous evils. Infanticide should be legalized because once in a great while it might save the life of the mother, they say. Child mutilation should be legalized they say, because once in a great while someone is born mutated because their mother smoked crack or their parents were related. Tax slavery should be enacted they say, because some people are too stupid to make sound decisions. Normal people should be forcibly disarmed and forbidden to defend themselves they say, because lunatics snap kill people sometimes, nevermind that it's the liberals who allow the madmen to roam free.

Every time you see a liberal claiming something is a fringe case, the truth behind it is that they are arguing for the normalization of evil.