Here's a recent example from a YouTube comment:
Majorbakstor: And that utility is based on the resistance of death and suffering, increasing the chance of survival and well-being. Anything that goes against these standards is immoral because it goes against the moral standards that prehistoric human beings required in order to survive at ALL. I recommend you studying anthropology and philosophy before you go spouting off about morality.Operating from that presupposition, I briefly examine homosexuality. Homosexual relations lead to non-procreative relationships between humans. The species' chances of survival are reduced to the lifespan of that generation, and only that generation, as there will be no offspring. The human race ceases to exist, or at least suffers damage to its evolutionary competitive fitness, as there are fewer humans to be selected from and thus it requires fewer disasters, fewer diseases, less predation, etc, to bring about the end of humanity.
Thus homosexuality is morally wrong, given this naturalistic evolutionary framework.