You don't really gaslight him though. He's basically a already bi-curious dude, but from a more conservative culture where "men fuck girls and girls fuck men and they make children together" mentality is heavily ingrained, being a "species" from an enclave and all.
So you don't really turn him gay/bi, you're just helping him explore himself and what he likes, and it turns out that includes enjoying getting his ass pounded enough for him to cum twice from it.
Apparently in V3 the gaylsol interaction is gonna be changed for the better into something that's a bit less "dubious consent" as well.