Straight men like shemales because they are/appear "feminine" and "most" shemales etc. like straight men who are typically masculine because they want to be treated as women. "Most" transgenders want straight partners. "Some" straight men can get turned on by "gay men" that have very "feminine" (I think people call it "flaming" )qualities and the guy can be sporting a goatee.
It looks like a duck, smells like one, walks like one and quacks like one. So to the human brain it must be a what? A duck. That's why "some" guys fly off the handle if they are ever fooled by a transgender; transgenders confuse the natural male senses for what's considered female and masculine. Most guys at this point (since he has a woody) doesn't know whether to bang the hell out of her; or punch her in the face and throw her out. I'm not an expert, just my 2cents.