Sorry, I have to warn you that you're talking to a lawyer (me).
I doubt that "murdering" animals is a problem unless the animal is also an endangered species.
"Raping" animals is, as far as I know, always illegal. Heck, it's also illegal to have "consensual" sex with an animal -- assuming that's possible. In other words, sex with animals is always illegal.
I guess we're on a slippery slope but this is my usual state of being.
The person I quoted complained that the pro-life side worries about the abortion and research on humans without ever explaining why humans are special. My point is that we have laws against murder that apply to humans and not animals yet I don't see people navel-gazing about why we simply assume humans are special and only loons seem to think that its as OK to kill humans as it is to kill animals or that killing animals is murder.
As for bestiality, the legality varies by state and it's notably not illegal in several states (as a recent "accident" involving a man and a horse with the man dying from injuries sustained illustrated) and since animals can't give consent, arguably any sex with an animal is rape, yet I doubt you'd see sex with an animal, even in states where it is illegal, prosecuted under the same states that govern unlawful sex with a human.
To put this in terms that a lawyer might understand, the host of statues that make doing certain things illegal to others assume that the other is human and would not pass even be accepted by a court if the victim was an animal rather than a human being.
True, but I'm not aware of any civilized jurisdiction that punishes bestiality as severely as it punishes rape. (Some places will execute people for the former, and more reasonably will do so for the latter as well, hence the "civilized" proviso).