This is not meant to be offensive to gays...?

Honestly, I love my gay friends too much to risk offending them with this so I've decided to ask any random person who'll answer. I seriously do not understand this WHATSOEVER. Try to keep up. Ok, if you're gay and dating a transvestite does that make you straight?? But, then again, isn't the whole point of being gay/lesbian because you're attracted to a certain body type? So, if you're gay and dating a guy who's turned into a girl, what's the difference from dating an actual girl? Wouldn't it all just come down to the fact that you're into that person emotionally and not physically? Then what's the point if being gay? Couldn't everyone just be bi then if personality is all that counts? I'm honestly curious and this confuses the hell out of me. Again, this was not meant to be offensive but there really was no way to sugarcoat it.