You have seen male dogs enjoy anal sex, bullshit. A male dog actually managed to penetrate and know another dog, and that dog enjoyed it?Um, what? I've seen male dogs hump other male dogs. Of course homosexuality exists in nature. What doesn't exist in nature is religion. Only human beings make up imaginary sky fairies.
In your mind homosexuality is simply dry humping? And of course, that must apply to female dogs, you have seen them perform cunnilingus as a preference to mating with male dogs?
There is no argument for your kind of ignorance and such a very loose definition of homosexuality. Of course if we go with your definition, homosexuality is certainly an animal behavior which is an abnormality in human beings.