This logic makes no sense.
Seven is a symbol of sexism by the fact that she was just here to be a sex object. I dislike the character (partly, as I mentioned there are a lot of reasons to hate this shitty character) because it is the typical product of sexism where the woman is supposed to wear hills and show her boobs, even if she's a braindead robot.
I am judging the character by the purpose of it. There is no person that I'm judging, I'm attacking the concept and the people who made it.
Also, I struggle how it is sexist considering that it's unrelated to gender. Harry Kim is an equally bad character that was just put here because the actor was elected sexiest man of the year or some other stupid shit like that; the difference being that he was not put as a central character, and didn't completely destroy the coherence of the show.
On a side note, I really don't understand what is the goal of trying to say that pointing out sexism is sexist. You'd rather have people not point out anything and let sexism happen freely? Now that sounds sexist.