Same logic applies to muslims and feminists. No exaggeration, I can't tell you how many times I've heard some who call themselves feminists claim others who call themselves feminists "aren't real feminists", and then the latter says the same thing of the former.
Not one single person here, from either political side, (you and me included) avoids over-generalizing, because as human beings we can't function without generalizing to a degree. But there are far too many on both sides (and I won't claim either side has more or less, because that would be too debatable) who actually believe the generalizations fully apply to every single person being generalized. Like anyone only moderately right of center (or even LEFT of center) is automatically labeled an alt-right nazi. And I'm sure you could name generalizations on the left.
Another problem is that 4chan has been granted too damned much power, and far too much legitimacy has been given to their trolling, to the point that too many people now actually buy into that hogwash that milk is racist. Denmark or Sweden has even officially labeled it as such.
Or the way the thumb-and-forefinger "Okay" symbol has been called a "white power" symbol thanks to 4chan's trolling, and now it wouldn't surprise me if some "punch a nazi" leftist attacked Kavanaugh's wife over nothing more than an unusual looking way she held her hand when she crossed her arms.