It can happen. It’s in the fine print of your ticket. The ship captain has complete authority to toss off any passenger for not following the rules.
According to this story, a passenger was upset because he couldn’t get into a show. He called the crew member and idiot. The crew member called for security. The passenger said it better be more than one security member because he was a big guy.
The next port was Tortola and he was escorted off the ship and had to pay his own way back to Florida.
The captain is judge and jury and there is no recourse.