I did find an article about a small town somewhere down south that tried to ban Am.Staffs. from herding trials. Their reasoning was that the Am. Staffs. won all the ribbons and did not give the Aussies any chances. They did not achieve this goal.
-EDIT- Am. Staffs. and German Shepherds are both considered difficult to train as herders because they both have the instinct to bite the sheep instead of nip like collies do.
Now you are just are being silly. Herding trials that are open to the public (vs. Clubs) typically make people sigh a wavier and if you dog injures an animal you bought it. If anything Pitt aren't being allowed to enter because they are tearing up the livestock.
What do think the "Shepard"part of German Shepard Dog means? There are different "styles" of herding. A GSD and a Collie work differently that a Border Collie & Aussies, which is different from a corgi and a cattle dog, and none of the "work" like a Catahoula.
I understand you love your Pitts, I got it. Seriously, stop with the fairy tales.