I think the key is to put a face to the faceless.
JW art (not subliminal btw) paints those who are not JW's as angry, evil, dishonest persons.
The people JW's call on typically are nice, law abiding, loving, and family oriented.
The key is to get them to see the people at the door as people, instead of cartoon characters out of a WT that are going to have piano's fall on their heads.
"Can it really be that a confused teenager will be destroyed by Jehovah? Do you think Jehovah will destroy those who thought that the generation who saw 1914 would see Armageddon? That was wrong, just like other dogma JW's show are wrong? Whats the difference?"
Blood is a little harder to reason on, its such a "demonized" subject. But I like the attempts I have read here so far.