I think we need to remember that a lot of this thread is rather unscientific speculation. We're trying to figure out how people think--and remember, these are cispeople who don't view this question the way we do. If we really want to know what they think, the best thing to do would be to ask them. But I'm not sure how good the answers we'd get from them would be. They may not really know. People don't always know why they think what they think.
I base my view on the fact that you will hear trans-haters call us "sick" and "perverts". If I remember correctly, a 1913 health act in the US labelled us "moral deviants". But I don't think I've ever heard a trans-hater say, "You're lowering yourself by trying to be a woman." But I don't claim that I have any scientifically-gathered data on this question. I wonder if anybody does.
We could come up with all kinds of theories. E.g., a man is supposed to be strong. When he dresses as a woman, he's not projecting an image of manly strength. I myself would like some real data before I come to any firm conclusion.
Annabelle