Why in nature are some animals "gay" and have to  go with it or die and when some humans are "gay" the religious say that it is not "nature" that made a human gay  but the human chose to be that way?
Most barnacles are hermaphroditic.  (Each individual barnacle both male and female).The ovaries are located in the base or stalk, and may extend into the mantle, while the testes are towards the back of the head. 
So if animals with no ability to reason have no choice in how they are designed by nature sexually then why would humans have to?