Just a thought

Anytime I have a discussion either in person or online, I hear a common point offered by homosexuals and their supporters. The point being, homosexuality is not unnatural because it happens among some of the animal groups. That is the end all argument that cannot be countered (at least that is what they believe). I thought about the logic of this argument and came to an interesting conclusion. Is it acceptable among people because it happens in the animal kingdom? If that is the case then I have a question. Many animals eat there young, so is it okay for human parents to eat their offspring?