My parents are sometimes disrespectful to my dog?

Knowing that your parents don't like your dog, you can anticipate when they might "disrespect" him and be proactive about it. If he wanders into a room where your parents are, call him in a cheerful voice and take him to another room. If he drips a little on the floor, be right there to wipe it up before you dad discovers it. Be his little guardian angel for his remaining years. It might make a difference to him and I know you will feel better about it.