We have a 8 1/2 month old Border collie and he LOVES Tyson. The problem is he loves him a little too much and he's playing a little rough. Not biting or anything but he doesn't realize how big he is and keeps knocking Tyson over and we would stop him and tell him to play nice or not be too rough which he would do for a little bit. After he would calm down Tyson would go right back to Jackson (our border collie) like he still wanted to play so we decided not to stop Jackson and see what happened. Tyson growled a little the first time then growled and snapped aggressively toward Jackson. Should I let him do this since I know this is his way of standing up for himself or put a stop to it now before it becomes a bad habit. It wasn't a playful little growl either.