Or think of it this way: if he is the kind of person we want to drive away instead of help better fit into our community, then where are we going to find those "better contrarians"?

In my experience you don't find 'better contrarians' among people who are naturally contrary and have a chip on their shoulder. A good contrarian will mostly agrees with stuff (unless the community they are in really is defective) - but thinks things through and then carefully presents their contrary positions as though they are making a natural contribution.

Don't seek the contrariness. Seek good thinking and willingness to contribute. You get the contrarian positions for free when the generally good thinking gets results. For example you get lukeprog.