I don't think our fetishes are unnatural: being non-average or non-standard doesn't mean non-natural.
There is much variety in nature, and maybe we're way out on a tail of a normal distribution, but that's still only natural.
As long as we don't harm others (physically or psychologically), I see no problem (apart from social acceptability).
Obviously, the pleasure centers in our brain respond to different things than is the case in the majority of the population.
Brain researchers are still a very long way from understanding how neuronal circuits work, and how flexible or versatile they are, so no one can really tell what causes our preferences.
I'm comfortable with the way I am, and just enjoy it without harming anyone.
