ribit,
I don't KNOW fragmenting alone would work, but it should be a lot faster and cleaner than going door to door with guns. Just split things up and let minorities vote with their feet. I think MOST people would either shift beliefs (more than you think, I think, as most people are herd animals) or MOVE.
In the case of the Civil War the country was MASSIVELY split by region. It remained mostly split for 100 years afterwards as well, and might have continued that way absent new technologies which really intermixed populations culturally and in physically.
In the case of the Revolutionary War the pro and con were pretty intermixed, as is the case now, and a lot of people chose to leave:
•1 in 20 able bodied white free males living in America died during the war
•24,000 British Soldiers were killed during the war
•100,000 Loyalist fled to Canada, the Bahamas and England during the war
•45% of colonists fully supported the war
•20% of colonists were outright loyal to Britain
•3 million is the estimated population of America in 1776
http://jalopnik.com/the-revolutionary-war-by-the-numbers-1600199390
So ~600,000 British Loyalists had to figure out how to live with a government they opposed -- to to leave. Sort of like the whites who stayed in S. Africa, and rather how I feel about the current system. I'd rather move to Florida or Texas or Idaho, or someplace , I don't have to life with Zombies and Vampires and Worms.