I know we're supposed to side against this woman because going off on a store employee is a super shitty thing to do, but come on — have you ever been to the Genius Bar?
To be honest, I've never understood why people think this is an effective tactic. I've gotten so much more out of simply being polite and kind to others than I ever could get out of losing my temper and going on a tirade.
I have lost my temper on the phone ONCE. It was with United. They lost my bags and didn't fix it for like 5 days, and I told the phone person (poor lady, I feel awful in retrospect) that "this bullshit was everything that is wrong with legacy carriers." She ended up giving me $50 in vouchers as an apology.
It wasn't worth the cost of her dignity or mine. I have never done anything more than strongly word a complaint since then. It's worked out well for me, because I'd rather keep my dignity than a few hundred bucks over my lifetime.