I agree it is in very poor taste to yell at anyone customers included. I'm just saying look at it from his perspective. The mature thing to do would be to go back, explain yourself, apoligize and make amends. If he still wants to be a jerk, I wouldn't go back either. I have seen it from both sides of the counter, and perspective makes a difference. Theres no reason to hold a lifelong grudge over a simple misunderstanding.