Ok how about everyone be honest with themselves and I guarantee there is a professor or two that you wouldn't need the good grade incentive to do something like this. I will be the first to admit I had a very attractive psych professor who I would more than like to have "gotten to know" if I met them at a bar and not in class.
And using murder as the example of how ends don't justify the means is about the worst example you can use...self defense.
Exactly with regards to the last 2 lines of your post. Same with stealing being a bad example. One can argue that a poor person on the streets esp. in developing nations sometimes are put in a position where stealing is the only way to get food short of begging esp. when we have untrained little kids on the road. So its not that black and white. Rape, that's another issue altogether. there is nothing in the world I can believe that can justify that.