By leaving your mechanic's shop, you opted out of the "scream and yell" script. You didn't want to play by the ape rules. They were baffled because in their mind, the person who shouts the loudest, gets his way.

Look at people who interrupt - they know someone else is already speaking and the interruptor increases his volume until the other party, not wanting to look a freak, gives up. The shouter gets his way and the behavior is reinforced.