Please edit your post to remove the gamertags as naming and shaming is against the forum rules.
That said, I'm sorry to had this experience. At a guess I'd say they were probably waiting for a 4th player to join them and tried to get you to leave to make room (as far as I know you still get gold and rep from voyages while in the brig, so it wouldn't have been that). It's one reason they introduced the 3 person option as this was happening a lot in testing with people who didn't want a 4th crew member.
I think it was mentioned in the latest Tavern Talk that they will be introducing a feature to hold crew spaces for friends in the future (thereby resolving issues like this), but that it's quite tricky and can unbalance the game a lot, which is why it wasn't introduced at launch.
