Not true.
Males "have sex" with toys and blow up dolls, without being attracted to those things, for example; pretend with their minds, etc.
Although that does not fit with the guys who get married to a female have kids and then suddenly "have to be true to themselves" and get a boyfriend. That would make it a choice and we can't have that so we will not bring it up.
I agree that humans can choose to have sex with any number of things but the key word there is choice.
If you a guy and you can choose to have sex with a girl you are not hardwired to be "gay".
If you are not hardwired to be gay it is not genetic.