AFK/typing = Free points. Been my policy ever since I started playing games online.
I see no reason why I should refrain from shooting AFK players, especially when any other player could (and frequently do) shoot them. Any player has the same opportunity to shoot someone who's AFK, so it's not cheating, as any player can do it just as easily. Yeah, there's an element of luck being next to the typing/afk person at the right time, but there is a ton of luck in any game of this nature. Just think of it as an Armageddon Shield, just sitting there. You're going to bash the monitor, right?