You know, my pit is super good with my cats and bunny. She doesn't chase them and has never tried to harm any of them. One of the cats was a kitten when we got her, and she bonded with tally (the pit). They sleep together most nights, with the cat curled right up against the dog.
I know this is going to sound crazy, but the bunny and two of the cats came to us before they were even weaned...they were tiny. And Tally was allowed, very gently to sniff and nuzzle them. Somehow she figured out that she wasn't supposed to play rough with them or hurt them, and that they weren't squeaky toys to be dismembered, but that they were part of our family. She cries at night if the cats aren't all inside the house at bedtime.