Does anyone really believe that a suicidal pilot won't be able to intentionally crash the aircraft if they're the pilot flying just because someone else is on the flight deck?
The PF of Atlas 3591 did a bang up job of it with 2 others on the flight deck with him, and he wasn't even trying...
Not dismissing the other arguments against single pilot ops, but keeping a suicidal pilot from crashing just doesn't wash. If they really want to crash, they'll do it. The two people on the flight deck at all times was just a feel-good.