Bestiality, in case you do not know, is having sex with animals. Bestiality is almost universally treated as wrong. But I fail to see why it should be wrong. There is not a single argument against it that is worthy that I believe out of all the things I have considered bestiality is probably the easiest to defend. The only reason why it is so high on my list of supposedly wicked things is because of the people's perception of it.
Bestiality, in my experience, sometimes comes up in discussions regarding homosexuality. Those people who are in favor of homosexuality and gay marriage are targeted by their opponents who say, "today it is homosexuality and tomorrow it is bestiality". Of course this is nothing other than a slippery-slope argument. The whole issue of gay marriage is that homosexuals are people too and so can enter into contracts, if we respect the rights of people, then we should respect the homosexual's right to get married. What this has to do with bestiality I have no idea, so the objection to homosexual marriages because it will lead to bestiality is a stupid argument. But my typical response to this slippery-slope argument is generally different, I do not use my counter-response above, I simply ask "so what?". Obviously, I use such a response to shock these people some more for my own entertainment but it does have a point nonetheless.
What objection can there possibly be to bestiality? What I always hear is that "bestiality is morally wrong". But why? I never hear anyone explain why this is so. I want to hear a secular response to why it is wrong. I do not want to hear religious responses because religious responses can be made to be into whatever we choose them to be. I want to repeat again, what has been one of my main themes on this blog, that there are no objective morals. So really my question should be interpreted as, "under what system of secular values that you use for yourself does bestiality become wrong?".
I guess a popular response, that I hear but am unconvinced by, is that bestiality is unnatural. It seems the secular value system is that whatever is natural is good and what is unnatural is bad. But this is a stupid value system to begin with. First of all, what does "natural" even mean? How can something possibly be "unnatural"? If something already exists then it is part of nature so how can we call it "unnatural"? Second of all, ignoring this big hole in this system of values we have to arrive at the conclusion that vaccinations are wrong because vaccinations are man-made, and are therefore unnatural (at the moment we are ignoring the whole meaning of "unnatural" for sake of illustration). Third of all, some animals have sex with animals of the different kind, this happens in the animal kingdom, therefore by definition those animals are committing bestiality, thus, does it follow that bestiality is acceptable because it is natural? Whatever, I am done with this non-argument, it is a silly argument, moving on to something more interesting.
The only remaining argument against bestiality that I can think of is that bestiality is violence against animals, and therefore it is wrong. This system of values does consider animals to have value and causing them pain is treated as wrong. And I do share in this system of values. I do think it is wrong to cause suffering to animals because they are creatures that have some degree of consciousness and feelings. However, when someone commits bestiality with animals he is shoving his penis into them, not some hot iron rod up their anus. The penis is tiny when compared to, say, a horse's penis. A horse's penis is far larger than man's, if that kind of penis, when enters into a female horse, is not painful (even pleasant) to the female horse, then clearly the human penis cannot possibly cause any pain to the horse. Also remember that animals never ask each other for sex, the male horse just walks over and has sex with the female horse. There is no consensual agreement between animals. For those reasons, if we stay consistent, it is not wrong for a human to have sex with another animal.