Animals do not possess our faculties. They cannot be expected to advocate for their own rights beyond a basic fight or flight level, so when we interact with them, we must take responsibility for their well-being. This means not raping them. (I hope no one actually needs to be told this. Do not rape animals!)
I’d like to address some of the fundamental issues your question brings up. Atheism doesn’t have ethical consequences. Of course, since there are no gods, morality can’t be defined with reference to gods. This is a sort of “meta-ethical” consequence of atheism; it’s “meta-ethical” in that it tells us more about where our ethics come from than what our ethics should be.
My point is that atheism doesn’t entail ethical positions on the rights of animals, women, minorities, the poor, dead white landowners, etc. You have to get your ethics from somewhere, of course, but “not god” is hardly a useful source (any more than “not triangles” would be). You know that suffering is hateful in yourself, and you know that others will also choose to avoid suffering, so a society that cooperates to reduce suffering (increasing happiness and liberty, etc.) is in all of our interests. Ergo morality.
In particular, rape is terrible. Rapists spew suffering on the earth like few others can, and they must be stopped. One of the essential aspects of rape is the absence of informed consent; animals cannot give informed consent, so having sex with them is abominable.
Posted: May 2nd 2012
See all questions answered by George Locke