I think that is something you and his wife would need to work on, seems like a problem within you guys if he's not doing anything to deserve such treatment. Can you think of any reasons for you treating him badly? if you do a little digging around in your mind you might find something. But yeah the therapy sounds like a good idea.

Not sure there is a certain personality type that attracts this, but I know a lot of people who try to treat others well and don't go about trying to cause trouble who still get treated like crap by a lot of people.