There comes a point with any ideology where you have to turn round and say "actually, no, you're not an XYZ."
So, for instance, someone who says "I'm a socialist, but one who believes in off-shore tax havens, less tax for the very rich, banning trade unions..." - it's quite acceptable to say "You are not a socialist, however much you utter the words."
Or someone who says "I'm a Christian, but I prefer the bits about an 'eye for an eye' and stoning homosexuals to death to those pesky bits about loving one another, and I think apartheid white South Africans were right to interpret the bits about 'children of Ham' as giving Biblical support to racial segregation, and as for slavery, well it was good enough for Solomon..." - it's quite acceptable to say "You are not a Christian, however much you utter the words."
Similarly, if someone comes on here (with the express intention of being goady) and says "I'm a feminist, but I believe patriarchal family set ups where the man is head of the household are fine" - well then I'm going to turn round and say "You're not a feminist, not in the slightest, not one teensy tiny bit of a feminist."
Feminists can disagree in good faith, for instance, about prostitution (some liberal feminists argue for legalisation from a point of view of harm limitation) or even pornography (some liberal feminists argue that the problem lies not in porn itself, but in the conditions of its production, and that a blanket ban damages women's fight to reclaim their sexuality in the face of being sexually repressed by men with a madonna/whore complex). I don't agree with them, but if they're arguing from a starting position of "how best do we liberate women from male oppression?" then they can still claim to be feminists.
But any woman who thinks there are circumstances where a man should be boss of a situation simply because he is a man? Nope, that position is never, ever a feminist one.