If  surveys are correct that at least 20% of priests are gay, then it would follow that rape of boys would only be 20% of the total number of rapes by priests.   

But the rape of boys by priests isn't 20%.    It's 80%.   Since the 1950s, 80% of the cases of child rape by priests were same sex attacks.

This can only mean that gay priests are far more likely to sexual predators of young people.   Heterosexually oriented priests, as a group, tend to be far less a risk to children.