It is understandable to want to protect your friend's feelings.
Jake hears Amanda telling his friend Bryan that he's a total idiot.
Jake wants to respond to Amanda's accusation.
Jake says that Amanda is wrong, and needs to back off of Bryan.
Jake says that Amanda is right, and is actually being nice, because there are a lot more things she could say about Bryan.
Bryan feels happy that Jake defended him, and their friendship grows stronger.
Bryan's feelings are hurt, and he feels like he's being ganged up on, and pulls away from the friendship.