Exactly. And watching it from a different angle it looks like Nelson gave a small push-off to Munchak when he was trying to go after the other player.He didn't do anything wrong.
Nothing special about pulling hair. It's not considered anything but uniform.
And the tussle was 2 parts. First part was Munch trying to help Nelson by catching him. Second part was holding him back from trying to get in the player's face.
If he had just turned around and went back to his huddle, nothing happens there.
Good on the league to realize that.