Milligan takes certain liberties with the League in this story. The characterisations may not ring true for some since Milligan amplifies certain aspects of each character. We're meant to see them as... not 'types' or 'icons,' but as something different than what they normally are. They represent broad groups, while also coming across as more human and petty. In many ways, a more realistic representation of a group like this and the personality conflicts that come out of it.
The main conflict is that there is no leader of the Justice League here. There are people who think they lead the League, like Superman or Batman, who feel that their opinions and decisions should inform the actions of the other members, but that's not the case. What penalty is there for acting autonomously? The League splits on how to handle Frank's emerging powers with the Flash and Green Lantern quick to argue that they should "destroy" him, even when his human side is raised ("HUMAN LIFE? IT'S A CYBORG.") Wonder Woman and Batman want to observe him, wait and see what he chooses, the Martian Manhunter wants to reprogram him, but Superman decides that they should wait. Except, that's not what happens exactly. Wonder Woman informs Frank's girlfriend of his true identity/history, causing their break-up; and the Martian Manhunter invades Frank's mind to get a read on where he's at. In each of these instances, another member of the League raises the point that they acted outside of the League, but, as J'onn says, "I WASN'T AWARE I NEEDED AUTHORIZATION TO USE MY INITIATIVE. [... WE'RE A TEAM] COMPOSED OF INDIVIDUAL, AUTONOMOUS UNITS." In short, the League is a democracy, which means that every individual has the right to choose their own course. The line that sums it up best is said by the Flash after it's revealed that Wonder Woman talked to Sara: "FUNNY... I DON'T REMEMBER US HAVING A VOTE ON THAT ONE."
The interactions between members of the League here are filled with sarcasm and bickering, which comes to a head when they fight Frank at the end of the story. Frank, as I said before, has the additional power of replicating the League's various personalities, and uses that to take down each member one at a time. He attacks them psychologically as well as physically, first destroying their will to fight and then beating them. That is, until Batman uses those various personalities against him by pitting them against one another inside Frank's head just as we've seen them arguing throughout the story. The League begins to argue with one another, revealing inner tensions and problems, spurring Frank on until he blows up, unable to deal with his own schizophrenia, basically. Before he dies he lets spew a confluence of statements:
BECAUSE YOU HAD IT EASY, SUPERMAN.
TRY BEING HUMAN FOR A DAY. NOT INVULNERABLE. A LOT SLOWER THAN A SPEEDING...
WE SHOULDA TAKEN HIM OUT RIGHT AWAY!
YOU CAN RUN, BUT YOU CAN'T THINK.
IF YOU WERE MARTIAN WE COULD TELEPATHICALLY BOND.
IF YOU WERE HUMAN YOU WOULDN'T BE SO CREEPY.
AND THAT NAME. SUPERMAN? TALK ABOUT EGOMANIAC! WHO ARE YOU KIDDING?
Frank reveals some inner thoughts of the League regarding its members, ones that barely go unsaid by the characters themselves up to this point.
After Frank's death, the Flash declares triumphantly that they've won, but Batman isn't so sure. That the Flash addresses Batman then as Socrates (Frank's nickname for him), immediately points to where Batman is thinking: they defeated Frank by demonstrating the disharmony of the League, all of the petty little bullshit that really exists. All the League did that day was defeat a schizophrenic man and bicker like children.
Is this the Justice League that fans are used to? No, but it really does ring true, working off Grant Morrison's conception of the League, which did have some of these issues, but never laid so bare. The League is not a team in the true sense: there is no leader, no real need to work together, no dependency, no trust... it's a collection of superheroes that pretend that they're all equal and working toward the same goals. But, democracy doesn't work for superheroes. I'm left wondering if the Justice League is really the United Nations of superheroes... a body that does good, but is actually ineffective in policing its own, in creating a unified agenda? Milligan raises some interesting questions in Kid Amazo... ones not easily answered.