If the superheroes were really benelovent, Joshua wouldn't have betrayed them.
You can see that Josh only begins to go wild after they tell him how it is all a scam. Before that, he was willing to play along. While he describes himself as a monster, this is more due to his self loathing. His dream was to somehow become a hero after all. You can still see this at the end, when he commits suicide and gets rid of Carrick. The only time that Josh had a free choice, he choose to do what he considered was right and altruistic, not selfish and evil.
