u/CountySquare9661

Think about it. Jack was one of the few survivors who hadn't committed murder by that point. Yet, in that same episode, he kills many Dharma members. You could say he justifies that by thinking that once he detonates the jughead it will all be undone and won't even matter. So, by that logic, if Sawyer didn't agree at the very last moment to let him do his thing, he probably would've killed him as well, since he believed his actions would stop their plane from ever crashing on the island and thus Sawyer would be alive and well either way.