It's not so dangerous if it's 2 player.
2 player games can bring people together.
Two player games can also cause a lot of arguments. "You MADE ME DIE!" etc.
I guess that could only really be in a game where you work in a team simultaneously against the computer?
Though even in that situation, it'd make you both die.
If person A is having trouble fighting the baddie he agreed to focus on, then his baddie is likely to kill him before he goes and kills person B.
(and that's still a rare situation, because often one player is expert, and could take them all on anyway. It would take a non expert and a real newbie to cause that situation where you both die)
I must say though, I wouldn't like to see a husband and wife in that situation.. husband is meant to be protecting his wife and she screams that at him. Or worse, "pathetic" husband screams that at his wife!
I've almost never seen a situation where Person A causes person B to die (while A still lives).
Sure, if person A accidentally hits person B and person B is low on life. But that's really rare. (if B was higher on life then it would take a more powerful weapon like an RPG, but they usually require aim)
What situations did you have in mind where players might shout that?
player A causing player B to die / vice versa. ?!