Boo's a rescue so we don't know much of what happened to him the first 4 years of his life, but he has serious issues with white German Shepards. Like your Tobie, he's fine with other large dogs. A dog park recently opened up just down the street from us. We've been going and Boo has been loving running around with all the dogs. I'm going to be curious to see if he has issues with other breeds of white dogs, or other standard color German Shepards.
If you've had Tobie all his life, then there is no telling why he has such strong feelings against Boxers. Sometimes there's just not accounting for their tastes.
