What gave you the right to define feminism?

You’re making an unexamined assumption. There’s a reasonable feminist case to be made that Kardashian’s prostitution of herself is unhelpful to women collectively. You’re ‘othering’ people who define themselves as feminists who also have an ethical objection to prostitution, and you’re doing it from upon a high mountain of self-righteous certainty to which you’re not at all entitled.