Yeah, NTS gets called all the time when it doesn't apply. It really is hard when a group is self selecting, because there is no way to reliably categorize people as in or out of the group. I find feminism to be a particularly tricky group for this; anti-feminists will find some way out there person who says they are a feminist and wants to kill all men. The anti-feminist will say, "Look, feminists want to kill all men! Feminism is horrible!"
If you try to argue that this person does not represent the majority of feminists, you will be accused of No True Scotsman.
I note that "this person does not represent the majority of feminists" isn't No True Scotsman for any definition of feminist. Someone can be a feminist while not representing the majority of feminists.
"This person is not a feminist" would be NTS for some definitions but not all.
If you try to argue that this person does not represent the majority of feminists, you will be accused of No True Scotsman.