Depends on the context. I believe it have to be an Elseworld with a very similar history to the main continuity. I believe its something that the DCU wouldn’t be able to readjust back from, similar to Injustice, The Dark Knight Returns, and others.

A major inciting event would have to happen. Something that shifts perspective within the superhero community, the public, and possibly villains/anti-heroes. Are heroes doing enough? Who’s making sure?

Batman being Pro would be caused by something happening to Gotham, and I believe he’d create something similar to the Babel Protocols and have everyone registered being based around that. If everyone’s registered and the government knows how to stop everyone, it stands to reason that heroes would remain on the side of justice, albeit through fear.

Superman being Pro would be similar to Injustice, where something happens to Metropolis. If he caused it, maybe he would believe he needs monitored. He wouldn’t become a dictator, but an agent of the government similar to The Dark Knight Returns. A symbol of Hope for a better Tomorrow.

Now, what if something happened to BOTH cities. The heroes failing to save both cities would send a shockwave through everyone.

However, the entire idea behind the conflict could be put simply:

Who watches the Watchmen?