itssmiletime
Potential
I agree that it would have been a horribly awkward scene to watch, absolutely. However, the way you make it sound isn't entirely accurate either. If Angel's life depended on, say, Willow's blood, or just some random, innocent person's, Buffy wouldn't have gone out and killed them. The fact that Faith was evil, was actively trying to destroy Sunnydale and kill people, made the decision a fairly simple one. Murder? Yes, it is, but with shades of gray. I know Buffy isn't god, but if one of Faith and Angel has to die, and Faith was the one who literally caused the predicament in the first place, I have no problem with it being Faith who has to go. However, as we saw when Angel drank Buffy, the Slayer didn't have to die in order for the cure to be enacted.
And just because Angel wouldn't mourn Faith, a few hours after she tried to poison him to death and essentially forced him to drink the love of his life, doesn't make him the "bad guy". When he fires at her, he shoots to wound. I think she even says that (I could be wrong though, haven't seen the episode in a while).
First off, I don't think that Angel not mourning Faith makes him a 'bad guy'. You can give up on a person and still not be a bad guy- Willow, for example, says right to Faith's face that it's way too late in Choices, and she was well in the side of good. When Faith goes out of her way to wreck havok- yeah people are gonna give up on her, and I think Angel did also for a period of time.
My problem is that Buffy went straight for the kill. Faith didn't have to die. As weird, implausible this may sound, I wouldn't have much problem if Faith was alive, and Angel drank from her, as long as he doesn't take it all, and enough for her to be alive. Better than Buffy's inital plan of killing Faith, and bringing her body along, that's what I have a problem with. She could have knocked her unconcious, stuck a needle in her for all I know, and taken some blood.
At the beginning of Five by Five, Wesley is standing up for Faith, telling Angel that she's still human, feeling guilty for having failed her (which he did).
How did Wesley fail Faith? Faith's first words to Wesley were 'screw this'. She disobeyed any orders. She's not a child. None of the scoobies let Wesley in on anything that was going on. They blamed him for pretty much everything (see Xander's comment in Enemies)