I think it's normal dog behavior to go after a wild animal in the yard. I don't think it's normal dog behavior to go after another domesticated animal. They seem to know the difference unless they have never been around a cat. Some dogs just hate cats though, it's hard to say. Can't say I blame them. Even though I have 2 cats myself, I can totally see why a dog wouldn't like them. My older cat is terrible to the dogs, lol. That doesn't give them a reason to shred them to pieces though, of course
