I don't think they are much different from other breeds in that respect.
I had 3 for a couple years. One was a grouchy old male, losing his hearing, long in the tooth, pretty quick to throw down with other dogs. I was concerned when I brought an 8 week old heeler into the house. That puppy pestered him relentlessly. He would scold the pup, give her a sharp bark and growl, but he would never actually hurt her. Many times I thought she deserved it because she was a major nuisance.
