Pointless and Dangerous
Ok, so we split the country in two and everyone can move to the side they want. What if someone doesn't want to leave? Forced deportation and property seizure? Will you have free elections? Will people be allowed to vote for conservatives? If they are born in your country, but have conservative views, are they stripped of citizenship? Will we just become the thing we don't like?
Maybe everyone will be happy for a short time, but history shows us that factions will develop again. Then what? Another split? Or just a good old fashioned purge? Better hope you aren't in the wrong faction. Or even if you are in the right one, you might not be later.
China had a civil war, the nationalists went to Tawain, and everyone was happy, right? You ended up with two authoritarian regimes, was that a good thing? On the mainland, you soon had factions develop. One faction is in charge for a while, but once Mao died, they put his allies (and even widow) on trial and handed down death sentences. And these people were presumably all on the same side.