We as human beings have risen above instinct and have something called a conscience, and reason, animals do what they do to survive, but unlike animals, we are capable of living, as in enjoying life. because of our own societal and technological advancements, we don't have to worry about absurd survival examples like the one you presented above. the reason why animals aren't raping eachother is because they HAVE to do it instinctually to survive, while we, as humans are capable of having sex for pleasure seeking, and emotional reasons. I should have read yours, and Exilement's posts more closely, and I apologize for being so ignorant
EDIT: @Leokill I couldn't give any less of a fuck if it is legalized or not, I'm just expressing why I think its wrong
Sorry, I would just like to address this point; my example was an illustration of your argument. It showed why your argument failed.
You cannot then dismiss it simply because we are in a state of technological advancement in which it would not occur; given that this is a debate regarding morality, it doesn't matter whether or not the illustration CAN occur or not. With the ethics being discussed change depending on the example? No. My argument still stands.
As for your counter that humans are of greater sentience, that again doesn't work; lets take another example.
Lets imagine that in the previous example, the girl was deaf. But the boy knew how to speak. Before the boy's mother died, the boy was taught what sex was. But because he has no way of communicating with the girl (this is a hypothetical example, just imagine they cannot communicate) or teaching her; so he knows what sex is on a mental level, and she knows on an instinctive.
According to your reasoning, no matter what happened any sort of sexual contact between these two would be considered sexual molestation. That's completely illogical. Ergo, your argument is flawed.
As for the fact that animals may feel pain; this is an issue perfectly addressed by J.S. Mill in On Liberty, perhaps the founding book on freedom. He argues that just because an act CAN cause harm, that doesn't mean it should be illegal; something should only be illegal if in every instance in which is occurs, it causes harm.
Take the sale of alcohol; just because SOMETIMES, alcohol can lead to traffic accidents, does that mean we should ban alcohol? NO! because there are plenty of sensible drinker, and we shouldn't remove their liberty to drink because of the actions of a few irresponsible.
Same applies to bestiality; just because some animals are harmed by it, that doesn't make illegalising the practice okay; illeglise the instances of harm, but not the practice itself. Hatchet Haro raises an excellent point about the fact that the animal within bestiality, if they are male, often takes an active role; this sorta ruins your consent issue, as even if an animal cannot speak, if it is actively fucking someone, you cannot possibly argue that it DOESN'T want to have sex with them.