MIB is beaten up by Jacob after revealing the truth, leaves for the other camp

As Mother lays sleeping at the caves at night, Man In Black sneaks in and goes to where Jacob is sleeping. He wakes Jacob up and tells him to come with him.

A short distance into the jungle, MIB reveals that he has all of their things and they are going to leave and never come back. MIB reveals that they are going to the other people on the island because they are their people. Jacob strongly objects, reminding him of what Mother told them about the people. MIB tells him that Mother lied about everything and Jacob has to go with him because he doesn't want to go alone.

The argument gets more heated as MIB says that Mother doesn't love them and she's not even their mother. With that, Jacob snaps and tackles MIB, repeatedly punching him in the face. Mother shows up and Jacob stops, leaving MIB's face bloody.

Jacob tells Mother that MIB is leaving to go to the other people. MIB stands, spits the blood from his mouth and says that he knows now that there is another place across the sea that is where he's from. He says he's going to go home. Mother asks who told him that and he says his mother, Claudia, told him.

MIB says that Mother killed Claudia, who was Jacob's mother too. He asks Jacob again to come with him and Jacob says "no." Mother stops MIB and says that no matter what he's been told, he'll never be able to leave the island. MIB picks up his bag and heads into the jungle towards the people.

Why is it that at this point in his life, Mother is saying that MIB can't leave the island? She said they couldn't hurt each other, but Jacob beat up MIB, so does this mean she's lying about a lot of things? Either way, MIB picked his destiny early in life and is on the path that he'll follow for many, many years.