there really is no equivalent of "raping someone for the greater good"
Actually, there is. The idea still exists in parts of the world that if your sister was raped, then the appropriate punishment is to rape the sister of the culprit.
On the subject of rape always being personal, I wonder if you couldn't object that rape is/was often a side effect of war, and that was never personal. It's simply 'take the women, take the land, destroy what your enemy is trying to protect'.