First, let’s define the term:
I’m going to try to tone down my own suggestions of body objectification, but talking about the subject matter tends to make the speaker appear as if an overly analytical/judgmental point of view is his or her predominant view on sexuality.
I would say that the most troubling part of the “beauty ideal” of the thigh gap is that it divides people where no division was needed, and it gives women anxiety for “not having the right body.” A cursory look at online forums and comment sections indicates both men and women expressing strong preferences for the sexual desirability of a woman with or without a thigh gap.
My opinion is that both camps are right – sexy women abound on both sides because… sexual desirability and the spacing of one’s legs have little to do with each other. I appreciate that there’s an aesthetic difference, and being very visually inclined, I do have sexual tastes.
I have an answer and sexual response to the hypothetical question of “If you conjured your ideal partner from thin air, would she have a thigh gap?” But I’m not telling because focusing the question on whether a woman possesses some quality or feature as determinative of a man’s sexual response or a woman’s sex appeal is a misguided inquiry from the outset. It’s an aesthetic question and only that and certainly not a question worth creating anxiety over.
So if an interested girl is unsure, and asks me if I like the look of a thigh gap or not, I tell her I like what she has between her legs, gap or not.