Unfortunately he falls in the 10% of the population who's minds will never be altered on the subject. All we can do as sportsmen is to continue to try and educate. Cut out a bunch of articles about the vehicle accidents related to deer, crop damage, etc........
And absolutely cook him some venison and serve it to him without him knowing it's venison. My mom is the same way about hunting and even fishing!!! Poor helpless fish with hooks in his/her mouth. Even though I practice catch and release (unless I really feel like haveing some fish) i suppose it's just something that we have to deal with.