Bro, premises of your argument is highly dishonest.
you are saying as if Islam is against the natural human behaviour and then, you go to question something which Islam does not forbade while saying it is also part of natural human behaviour.
I see a serious lack of coherrent thought processes, frankly.
So you are suggesting that religion goes along with human nature? I would say it teaches humans to act against their human nature and instincts. If a person spits on someone, human nature would dictate to spit back. Religion would teach you to have control, and not spit back.