Well, I'm not going to do a scientific study to prove it to be true, however if you look at for instance the number of heated debates on something like A2K; I'm sure you will see a discrepancy.
Maybe, maybe not. I'd rather not make that assumption about things I haven't seen. The larger the sampling, the greater the protection against selection bias.
Ah, but murder is murder. Period. Murder is one person taking another person's life. The end result is that another person is dead. Rape seems to be something subjective that is defined differently by different people.
I'm not so sure the distinction between killing and murder are so well-defined and universally agreed upon. For example, murderers are executed, and opponents of capital punishment call that murder. Vegans and whatnot say "Meat is murder." "Killing another human being is wrong," but, yeah, I'll send my kids to war. Is abortion murder? Depends on who you ask, and that's a pretty hotly contested issue, I'd say. Stand your ground and kill rather than run? In some states that's murder, in others, not. Looks fuzzier and fuzzier the closer I look at it. Not saying that rape is any easier to pin down, just that neither has a clear-cut, universally agreed upon definition. Hence, the controversy surrounding them both.