Why did Baldwin feel betrayed when he was conversing with McGinty in Scene 9?

I'm not sure where you are in the text, but Baldwin feels betrayed when McGinty makes him shake hands with McMurdo.... make peace.

“Tut! Tut!” said McGinty, getting off his barrel. “This will never do. We have a new brother here, Baldwin, and it’s not for us to greet him in such fashion. Hold out your hand, man, and make it up!”

“Never!” cried Baldwin in a fury.