You're saying that because it's not natural, it's wrong? Even if it's enjoyable, and the harms involved are accepted by everyone involved?
... Tell me something, do you happen to be wearing socks?
I don't think socks are natural.
This is actually a very interesting thing. When people start talking about "natural" and "unnatural", i get this twitching feeling in my neck.
The truth is, the horrific truth, which people saying this dont want to hear, is that everything we do is natural, else we would still be slime in the sea, if even that.
We can take cars for example, you may claim that cars are not natural, but unfortunate, something you have not thought about, we (humans) created cars, and now they are part of our society, daily lives, and so forth. Cars, have become natural for human lives.
If you start saying whats natural and not natural, you would end up in a very hard stool to sit in. As everything, could then be marked as "unnatural". Its not natural to have clothes, its not natural to live in houses, its not natural to have church weddings.. and so forth.
So to you people saying this, mentioning this, and all that, think about it, ok.