[chrisbennet]

The regulation caps what the airlines must pay, not what they can pay.

The moral, outrage isn't because United made a mistake. The moral outrage is because, rather than pay $800 more to correct their mistake, they resorted to force.

The moral outrage was compounded by the president of United not delivering a sincere apology. "I'm sorry your dog was run over." isn't the same as "I'm sorry I ran over your dog."

There seems to be a case to be made that United wasn't even in the right contractually. It certainly struck many people that way at a gut level i.e. when you take delivery of a product or service you don't expect the seller to come back later and take it back. This also contributed to the moral outrage.