I'm not a breeder, nor an expert, but I don't see the problem. 'Original' presa's have pitbull, bulldog and mastiff blood. (and Bardino) Crossing with Bullmastiff, Bandog or Bordeaux dogue (related to Spanish Alano) isn't so bad as it's all 1 family... Crossing with foxhound or GSD would be worse. And what is a 'pure' breed ? Falsifieing pedigrees just for the sake of money is a different story offcourse.