also, I think I would just say "listen asshat, don't touch my fcking dog again, I'm serious, if you don't like it tough...if you want to kick my ass, go ahead, i'll have your ass in court so fast it will make your head spin and no amount of steroids will stop the judge from putting you in jail and making you someones bitch, and if they don't do that i'll sue you for every penny you ever thought you had, don't fck with me"
then just leave it at that, if you get your ass kicked, well be ready for it I guess maybe have a witness with you when you tell him. And maybe he will respect you more for standing up to him, who knows but if your dog is like your child you would have ripped his head off already no matter what size he is.