Wait, did they try to redeem him? I thought it was only Charles who was offering to keep him safe/offer him a home at the school?
And yeah, the number probably isn't that big of a deal when he straight up murders 6 people in a pretty brutal fashion.
They absolutely redeemed him in the context of the film. If they didn't then while he's floating in the air helping Jean Grey rebuild the school, you would expect everyone else to tell him to fuck off, or for there to be a huge protest in the streets outside demanding him to be handed over as a criminal. Even the television report at the end was phrased as a sort of redemption story with the reporter commenting that it was said that he turned on Apocalypse at the end and helped to end the threat. It's really shameful!
The only real difference a number makes is: is Magneto worse than Hitler? So, the nazis were bad and "created" Magneto. At what point is Magneto worse? He must have killed so many innocent people at this point. The people who ratted him out probably thought he was a dangerous criminal who was escaping justice. But since Magneto doesn't think he should be helt accountable for anything he does or anyone he kills he's shown as more a genocidal maniac than anyting else. Both Days of Future Past and Apocalypse really have no idea of how to make his actions sympathetic.
Magneto isn't worse than Hitler because Magneto isn't real. I think that's the one thing that makes it easier to swallow. Lol.