The Island is NOT a Prison for the MIB by JPfaff

I have read a few theories and comments arguing that the island is a prison for the MIB. This makes little sense when you take into consideration the first season in the Season 5 finale.

First, the MIB ridicules and objects to what seems to be a repeated practice by Jacob to bring new people to the island. If the MIB were imprisoned on the island and wants to escape to the 'real world' so that he can do whatever evil things he desires, why would he object to this? First of all, even if he couldn't use them to escape, wouldn't it atleast give him some people to be evil upon? More importantly, what other way would he have to escape the island? New people on the island would mean new opportunities to escape. The fact that he objects to it so greatly demonstrates that he wasn't a prisoner. Since then, because of his disdain for the people of the island he might now want to leave, but it doesn't make sense that he was imprisoned here.

Second, if the MIB were imprisoned here for being an evil being, why would his objection to new people being brought to the island be based on their inevitable corruption and destruction? If anything, he would welcome and applaud such acts, and thus it would be a reason for the MIB to like them.

Third, after Locke / MIB has Ben kill Jacob, and the mercenaries (or whatever you want to call them) show up, why does he tell them that they are free now? He seems to be happy for them because they can leave now and are free. It is only after they attack him that he kills them. Their deaths are more of a self-defense act than murder, (or at the very least, an act of vengeance). If he was so evil, why not kill them right away if he was going to kill them at all? While the little boy in the woods may have been referring to Sawyer as a person MIB can't kill, such a warning was never given in regards to the mercenaries.

I think it is more likely that the MIB is more likely a pawn of Jacobs, and he doesn't want to be in that role anymore.