Feminism is an idea. Feminists, or the people who adhere to that idea, are a group. If every single adherent of an idea you encounter is an abhorrent person, most people will stop and consider if they want to associate with those people. Typically the answer is "No".
Most people will also wonder if something about the idea turns people into abhorrent people or if something about the idea is only attractive to abhorrent people. In either case, it is not something to which our notional person is likely to be attracted.
In short - the people who adhere to an idea are seen as commentary on the idea.
> Feminism is an idea. Feminists, or the people who adhere to that idea, are a group.
I would have thought that everyone who believes in gender equality is implicitly a Feminist..
> If every single adherent of an idea you encounter is an abhorrent person
Are you exaggerating for the sake of argument (perfectly valid), or is it that bad for some people?
But Feminism isn't a group; it is an idea. If some of the followers misbehave, you should still be able to believe and support in the idea.
To me, supporting ideas only when you "like" the (majority of?) people supporting them is akin to supporting free speech but only for the positions that you believe in.
(edit)
> Why do you feel compelled to couple it with insults?
I'm not sure where you're reading that. The "You" at the end was directed at the fictional person that I'm attempting to emulate with the 1/2/3 reasoning, not you.