Micah didn't really start getting in Dutch's ear until after the Guarma chapter, so it still would've all turned out bad without him there. Dutch was already leading them down a bad path before then. His basic philosophy wasn't that people should be free and civilzation was ruining everything, it was that Dutch should be free, and everyone should just follow him.
Wasn't Blackwater Micah's plan though? I think the gang really started going downhill after blackwater, it's collapse would've inevitable but slower without Micah to egg on Dutch at every turn ---
And when he gets to Heaven, to St. Peter he will tell, one more soldier reporting sir, I have served my time in hell.