The title may ba a bit stupid, as the game is told from Arthur's perspective, who clearly does not like Micah. But objectively, why is Micah any worse than the rest of the gang?
What people keep saying is that he is bloodthirsty and so on, but I remember shooting up Valentine twice (and a few more towns) as Arthur during main missions for no real and apparent reason other than wanting to escape, which is the same as what Micah does in Strawberry. Also, Arthur beats a sick Mr. Downes basically to death, just for a few dollars. During chapter six, but also before, he keeps shooting police officers, random people who just happen to work for Cornwall and also soldiers of the U.S. army who didn't even do anything other than patrolling.
During my last playthrough I just could not see why Micah is supposed to be any worse than say Arthur, John or somebody like Dutch or Javier.
He also antagonizes people in the camp, but at the same time, Arthur and the others keep antagonizing him as well, so I think this is kind of granted.
In chapter six, he becomes the rat, which is, from a gang perspective, bad, but doesn't change much, if anything, really, as the gang was on its last legs beforehand anyways, and which is arguably a good thing (bringing down a gang of murderers).
And, I mean, the entire gang is made up from criminals, murderers, robbers and con men, all bad people, so you really have to be horrible to be worse than them. What do you think?