Say that you go out of your way to do something for someone and you do the very best you can to do this favor for them. When you've gone through all the trouble of helping them and then they get pissed off at you because it isn't just "so" how would you react to their being pissed off? I mean HELLO--you took the time to do them the favor. It's NOT your fault that it didn't turn out just right.
What makes things worse is when part of the reason it isn't just "so" is because of THEIR mistake. And then when you show them their mistake, they come back and apologize.
Apologize? After an hour of ranting, raving and talking about it's your fault and that you intentionally caused things not to work out they way they were supposed to.
That's just bullshit. Frankly if it were me someone did that to, I would be downright offended if that person came to me and apologized after treating me like that, esp. when what they were upset about was caused by their error. No way, apologies aren't enough. And beyond that I'm not sure what a person can do to rectify their bad behavior.