Aside from my long rant before, while I thought the group was a bit out of character for kicking her out and it seemed like it was what Buffy needed, you can't ignore that the Hellmouth is messing with everyone right now. It's making them do things that they normally wouldn't do; this was evidenced at the beginning of the ep. People are leaving town, the school has been closed, there are fights all over the place and a bunch of cops actually tried to kill, not apprehend, Faith. There's enough proof that everyone isn't quite in their right mind and why everyone seems to be just a little off, including Buffy.