Wow, just wow. As someone who mostly flies UA, but enough on AA/OW to still make EXP, I occasionally venture on the AA forums, and am amazed by the level of victim blaming here! (It's certainly an order of magnitude greater than on the UA forums.)
In this thread alone, many posters have brought into question the OP's temperament / communication skills, repeatedly emphasized "hearing both sides of the story," and sanctimoniously tried to draw a distinction on valet checking / short checking (which would not be obvious to 99% of the flying public!).
Flying is stressful enough as is. The OP had a poor experience. We could all do well to show some sympathy.
Sometimes, commons sense and reasonable accommodations should prevail over complex, bureaucratic rules — and misguided ones like D0.