Sex is a dance between the dick and the brain, which evolves to learn the "most productive and least disruptive" ways to get a nut.
Usually, that means the following:
Most productive: a piece of pussy. They're abundant, they're easier to find compared to the alternatives, and they're far more socially acceptable.
Least productive: another man's flesh. Abundant yes. Available and socially acceptable, no.
Most disruptive: the price one must pay to become a fag.
Least disruptive: liking pussy doesn't render one ostracized, misunderstood, excommunicated, banned from society.
It's only natural most brains figure all this out and get with the programmed. It's also only natural some brains get it twisted, rebel, mutate, differentiate, retard, never get with the programmed.
But if the dick had no choice but turning to men, eventually, the brain would follow. Sex is an acquired taste, and if only men were available, men would acquire the taste for other men.
That's why men in isolation with other men, in prisons and such, suddenly become cocksuckers and butt fuckers. The brain adapts to what's available, same as when people stranded from civilization learn to live in ways and eat things they never imagined.
Sure, some won't make it. They're brains won't let them adapt and they die. But the majority, they'll find a way to suck it up and keep going, pun intended.
In a world without pussy, men and their brains would adapt, and soon enough, most men would be practicing homosexuality and practicing it a lot.