We've got people who say that when they carry, they will not under any circumstances attempt to save someone else's life if their own life is not in danger. People who say they would not take a shot on an active shooter. People who believe you should not be able to own an AK. All kinds of stuff, and it seems to have gotten much worse over the past few months...
I think there were even a couple of posters who would not shoot a man trying to rape a woman...
There's some caveats that you're not completely analyzing before engaging your shooter or rapist.
Shooter: This could be a plainclothes officer. You don't really know what he's shooting at, and you don't know what started the shooting. Engaging a target that hasn't engaged you might not be self defense when all the facts come to light.
Rapist: The girl in this case, or even the guy, could have a fetish for wanting to experiment with role-playing an alley rape. They could both be consentual in the act, but look otherwise. Stupid? Absolutely... but if you shoot him over it, you'll end up in jail, and sued for everything you own.
Not every situation is as clear-cut as it looks.
That being said, I'd also have an awfully hard time walking away from either of those situations if I could have a reasonable chance of changing the probable outcome. I know how you feel, but those other people on THR/TFL or elsewhere have thought their position out every bit as well as you have thought out yours.