Ironically, I'm currently editing a book manuscript by a former BaptIST minister who who walked away from organized religion and is now taking ReligionISTS to task over being divisive because of "their" insistence that everyone will basically roast in hell for not following their particular -ISM.

You're precisely right, -isms serve to polarize and divide, more than anything. And apologISTS for many points of view will skate by with the insistence that it is merely "human nature" to segregate ourselves into neat little boxes that include what we like and EXclude what we don't like.

I am, of course, an ideal-IST, so I am not convinced it has to be that way.