Speaking as a straight guy, I can state with a very large degree of confidence that homosexuality has never been an option for me. So, I can only assume that heterosexual sex isn't an option for a gay guy.
Mm-kay. What about so-called "bisexuals"? Or, ...
... I can state with a very large degree of confidence that homosexuality beastiality has never been an option for me. So, I can only assume that heterosexual human sex isn't an option for a gay sheep-lovin' guy.
How about that?