I have seen homosexual dogs. I think the issue is that when a homosexual dog mounts a heterosexual dog, the heterosexual dog takes offense to it and retaliates. It is much the same as any dog that tries to mount a female dog that does not want to 'breed' with them (whether in season or not). They fight back to say that it is unwanted.

Dogs do not have the same methods of advanced communication we do. Their method of asking is to simply try to start the process. Their method of refusal is to snap at them for doing it, possibly starting a full-on fight.

I have had dogs that will ONLY mount male dogs, even around a female in heat (especially around a female in heat). That makes the dog homosexual.