[kjc]

My dog did this. I wasn't being alpha enough for him so he started protecting me and going after the cats and other dogs. You just need to let him know that you are the boss and you have everything under control. Be more strict with him. When you start to disipline him for something, your energy level has to meet or exceed his. The first time will be the most dificult, but you need to stand your ground. When he misbehaves, say "Ah, Ah" loud enough to interupt what he is doing. If it doesn't work say it louder and be very firm. You may have to clap your hands, or make a similar loud noise to distract him. Once you have his attention, have him come to you and make him sit. Then tell him 'Good Boy' for coming to you. Then give him something to do away from where he misbehaved. You may have to throw a leash on him if he doesn't listen, and make him come to where you where. Never respond to him in anger and never hit him. Throw your emotions out the window for now. Your attitude should be one of no tolerance for any agression, and any behavior he does that you find unacceptable, and mean it. He doesn't know what you want him to do, you must show him, by interupting him, regaining control, and showing him what you want him to do or will allow him to do. If he doesn't understand, have a place for him to go away from everyone for 5 minutes or till he calms down. When he is civil, let him out again. Eventually he will catch on to the idea when he's misbehaving, he is separated from you and the family. When he is calm and nice, he can be with you. You will know it's working if he looks away from you or avoids you for an hour up to a day or 2. He'll get over it and come around, changed. This should not take a long time, maybe a day or 2, but you cannot let him slip or get away with doing anything you don't want repeated. Good Luck!

Also, keep in mind, it's not him you dislike, it's his behavior you have the problem with. Also, Vet check first is an excellent idea.