The fundamental difference in what you're proposing is a 'Comic Book Solution.' If you want to say that, because this world is a variant of DC, it should be treated with Comic Book logic, that's fine, but it's the author's decision whether to treat it as a comic book or a realistic world with people who happen to be able to fly and throw buses with the personalities of famous fictional heroes and villains from our world.
"A group of supervillains who are evil doppelgangers of heroes have doomsday weapons" is a 'Comic Book Problem', so sure, I'm proposing a 'Comic Book Solution'.
That's not an OCP for the Justice League. That's Tuesday. This isn't some "How do we deal with the introduction of new technology that radically reshapes the world's economy?" type of problem that's completely outside their wheelhouse. This is the kind of problem that righteous face-punching has been dealing with for decades.
They leave without preparing the world for their absence. They don't establish a long-term solution. Instead, they fix the immediate symptoms. The situation Paul has been appointed to fix is the extermination of an entire sector of society and the possibility of a long and bloody civil war. He's doing his best to actually fix that problem, one which the JL would only exacerbate badly.
Wow. You're getting an awful lot out of their plans and intentions by them simply walking in.
What you are essentially saying is that the Justice League is fundamentally incapable of dealing with a group of supervillains armed with doomsday weapons, so just their basic presence demands that they be taken down, and taken down hard, so that they don't interfere with the plans of someone who really knows how to solve the problem.
Now, I think that's nonsensical. However, if Paul is saying that, I think he's necessarily saying that this is
his world now, and anyone who steps into it better toe his line, and if he's saying that, he owns this solution. It's no longer "Eh, l'm doing the best I can with the limited amount of fucks I give about these people", it means that it's now his responsibility to actually fix things, since he's appointed himself the person in charge of deciding how things get fixed.
To me, the mindset Paul has here would say that, back in Paul's world, the Justice League should have given in to the Injustice League, the Light, and any other organization powerful enough to cause collateral damage in the course of dealing with them. It's the mindset that says that, if the Justice League knew that Paul was going to sneak into Eden or kill Nabu, that they'd be justified in taking him down to make sure he doesn't overestimate his abilities and fuck things up.
Talon's right that Paul wouldn't put up with that on
his world.