And I sometimes agree and disagree. The prisoner dilemma is a good RP moment. It destroys parties, but only that the players made a weak party.
For example, now I'm DM'ing a long campaign for three players. Half-Orc Fighter/DragonDisciple, Dwarf Monk and Half-Elf Rogue/Assasin. An Evil party (LE, LE and NE). I sent them in a demiplane of a philosophical monk and after some trials the monk had a dilemma. Three choices. He could help the other guys (they were in the middle of tough trials), but will hurt him (in the last trail, a fight he had -8 to hit). He could make the trials harder for them, but get 50k of gold (and that was a lot of gold for them, because they're lords of a town and need cash for it, for upgrades and stuff). The last one was... he could kill them, get their stuff AND get 1 million gold. Yes, one million. Even one of the players said "I will not hang it over your head, because of that amount of money." The player had a dilemma. He was Lawful Evil. What he chosen? The first option. After five minutes of thinking. This, and many other moment, showed that they know that they need each other, they will work together and achieve great things. If they didn't work together, they would be slaughter couple of times before. For example, one of the characters could die (he lost an arm in fight with an orc chieftain, but he sliced him in half), because an enemy army was attacking. What the rogue and monk did? They went for him and dragged him couple of days to a healer (he didn't wake up). Dilemmas are good. If the group fights each other it's because the players created a shitty party.