Humankind have a superiority complex. Many believe that we have the right, as people, to divide behaviour into 'Natural' and 'Unnatural' categories, yet at the same time we are always trying profusely to distinguish ourselves from nature.
Yes, it may be true that we as Homo sapiens are top of the food chain, but we are still part of it! Modern cultural figures such as 'Mother Nature' are presented as human in form due to the (often unconscious) notion that we are superior over nature. Despite this division between (Wo)man and beast however, any behaviour that a human commits that is considered deviant to the norm is suddenly labelled as 'Unnatural'.
Evidence of the superiority complex mentioned is the fact that we keep animals in zoos. Is the purpose of the 'Zoo' solely to capture the interest and imagination of visitors, or is it in fact a self-affirmation of our omnipotence? Human beings, whether we like it or not, are animals. Everything that is 'Man-made' is therefore in reality originally a product of nature, and isn't really 'Man-made' at all.
The reason I bring this topic up is because of how commonly the "It's not natural" argument is used today. When there is no credibility behind a point this is an easy-enough standpoint to adopt. In the area of LGBT rights, for example. Due to the fact that some people see anything that isn't heterosexual as wrong, they label it unnatural, despite the fact that humans are in fact the only species of animal that demonize other members of their species for their sexual preferences.
We have to accept that we are part of nature and therefore everything is effectively natural. We're not omnipotent overseers that can define what is natural and what isn't. Global Warming and even the recent floods in Britain are demonstrative of this. It may be angering that we're just animals, but at least it's the truth.