I'm pretty sure half the people b'awwing are doing it because he's religious. Oh no, god forbid a character follows religion, out of the, what, 200+ MINIMAL people in the series we see who wouldnt flinch at killing for kicks and giggles? Graham WAS evil, but after his 'baptism by fire' it served as an eye openening reemergence of his spirituality. To call Graham 'good' is not completely accurate. It's more he follows in his own way, but he will resort to violence to upholds what he deems good. But I believe Graham is better for Zion than Daniels evacuation.
I'm guessing the other half are b'awwing because Graham is critical of Eddie's Legion. I've noticed a tendency in Legion lovers to gloss around the edges; they had Graham figured as a monstrous man-mountain, spouting jingoistic jargon, killing everything with a glare, indestructible (well, that part was true) and generally making Lanius look like sloppy seconds. But above all, despite Eddie's betrayal, Graham HAD to still be loyal to the Sacred Ramblings. Basically, they wanted a character to reinforce their positive view of the Legion.
Instead, they got a human being who had a good think and realized, and stated in the game, that it was all a tissue of lies and barbarity (tissue of barbarity?).
I loved Graham. I'm bothered that he disappeared in my first playthrough, but that's what I get for helping Daniel.