It has little to do with religion, at least in the United States.
The primary reason has to do with physical dominance as a means to establish higher social status. Poor white culture and poor black culture are both very focused on proving yourself physically in terms of power and bravery. Anything that threatens the hierarchy has to be rejected and mocked, sometimes violently. It's why calling someone a "bitch" can get you killed in some places.
It's not just gender and sexuality. Being bullied for being too smart, for example, because it's a threat to someone's self-image and status.
I would guess that it's much the same in Africa, as strength and virility is a common way to determine status in poor cultures all over the world.
