It really is not all that different in the grand scheme of things. I think you would find that a large number of gay folks hated themselves (and plenty still do). Imagine you are in 1950s America and a gay guy, in a world where there are literally no other (known) gay men and that sort of thing just isn't talked about. Self loathing at your "freakish" urges isn't hard to imagine. I don't think it is all that different from trans folks.
The self loathing comes from self repression. They feel like they are a different gender. In a happy and loving world, this wouldn't be a problem. Little Johnny comes out as woman, switches clothing, gets some new hormones, and everyone starts calling Johnny Jenny. Jenny is happy in her skin, gets promotions at work, and no one thinks twice. That is of course, not how it happens. Johnny comes out as Jenny, and Jenny loses her job, stops getting promoted, and isn't allowed anywhere near a position that faces customers. The parents disown Jenny, people call shit at her in the streets, and even seemingly well meaning people struggle with pronouns and look and sound awkward when around Jenny.
Trans folks have it very rough. Gay folks can build their own little piece of America through friends and geography to escape the worst of the hate. Building an accepting world is vastly harder for trans folks.
Faking it until you make it is a perfectly acceptable way to do it, and vastly preferable to not trying. Most people who didn't grow up in a hippy liberal commune who are now easy around gay folks probably had to fake it until they made it to be comfortable. Hell, that is true with stepping outside any piece of your culture, regardless if it is race, gender, sexuality, whatever.