I have used the WWJD arguement lately. It is effective. It is hard for a JW to say "Yes, Jesus would DF someone for drinking 3 glasses of wine at a party and seeming drunk on 2 separate occations." I have used that exact example.
edited to add: since alcoholism is considered a disease and needs treatment, the last thing a loving, christian person should be doing is cutting off a person who clearly needs help. Shunning them into submission is not going to make them stop drinking. As I pointed out to the person I used this example on. The person who got DFd for drinking was an alcoholic and needed help. He only got worse after being DFd. She agreed and said no, Jesus wouldn't shun them and wouldn't cut them off; he would try to help them and the dubs are wrong to DF people for this and for smoking. No matter how bad smoking is for you.