I'll probably get flamed for this, but here goes:

DL, and their adoring fans on Airliners.net, constantly remind everyone how perfect Delta is. Prolonged exposure to Delta fans can be too much - sort of like how your stomach feels a little sour after you've had two pieces too many of Halloween candy.

AA, and their supporters, don't take American as seriously as DL supporters take their favorite airline. DL supporters truly believe that Delta is incapable of doing anything wrong, which makes discussion threads about Delta here (and, much worse, on Airliners.net), irritating. It's nice to have an honest, sincere, discussion about AA's strengths and weaknesses. We couldn't have a thread like this in the Delta forum, because the die hard DL fans would rip apart anyone who says anything even remotely negative about Delta.