Second of all. That's a rather sociopathic argument to make. That's no different than the argument made by some criminals who feel no guilt killing people because, "They were going to die eventually anyway, all I did was help them die a little sooner." I've actually heard people argue that people here, in the real world, have no other purpose than dying. Everyone dies, therefore it is everyone's purpose. At least, that's the argument I've heard. If that's what you believe, of course you won't take seriously anyone claiming to feel guilty after killing another. Heck, there are still people in the world that believe you haven't earned the right to be alive until you've killed at least one person to make room for yourself.
And third, this isn't just about guilt. There is a lot of anger at being used and frustration for feeling out of control.