You are way closer than what this writer made of the episode.

Also
''In the scene’s most profound moment, she posits that the meanest thing you can say to a fat girl is that she isn’t fat. And she’s right. The show doesn’t go on to explain why that is, but it’s not so hard to parse. To tell a fat woman—who’s fully aware of her weight, her size, her body, who gets up every morning…

''Vanessa is written in the most droll and likable way because C.K. wants to make it perfectly clear that the reason she is rejected is because of her size. Not even being the platonic ideal is enough when you’re an overweight woman.''

Can you imagine an 'ugly' man doing similar for a woman he was suddenly infatuated with? I think we can. I think that scenario has more to do with this episode than 'fatness.' See her manly fist pump when she go the date. Dude!

This is my interpretation too, though it seems most people are taking the episode straight. I don't think Louie the show or Louie the man is that obvious. He starts the episode with a bit about how women have the skills to reject men in ways that men can't. I think the rest of the episode illustrates this in some ways…