>>114090122Pim's arc is the best one in the pilot, anon. He's so far in denial that he forgets his family is a dysfunctional nightmare. His optimistic shield has holes poked in it by the party people rejecting him and calling him old. His defense is so flimsy at that point that Desmond's barebones intro to nihilism destroys him.
Pim grew up in a shithole. Deep inside, he knew Desmond wasn't going to be fixed by a superficial day of fun, but consciously accepting that was antithetical to his ultra-positive coping persona. Putting Desmond through a day of bullshit instead of leaving like Charlie suggested was pure selfish mental illness from Pim, and even Desmond knew it. That's why he promised to make Pim watch his suicide if Pim went out of his way to extend Desmond's suffering.