Then that manager will go to the OP's manager and say, tell your people to keep their noses out of my team. And if word gets out that the OP goes behind people

Then that manager will go to the OP's manager and say, tell your people to keep their noses out of my team. And if word gets out that the OP goes behind people's backs to tell tales, noone in the company will ever trust them again. The only way to win is not to play.