Since you didn't link not sure which you're talking about.
A Delta is banning bull dogs from flying because 6 died last year because of breathing problems that breeds (as well as persians for the same reason) are known to have. So it's a safety issue for the pet
B Pitbull dogs : Seems mostly because people are dumb and generalize a whole breed.
After watching Pit Boss it totally changed my mind on them.3nodding