@RayS I won't deny he DOES sprout inspirational lines, but they're way more organic than the usual examples I see. He doesn't radiate confidence, he's almost thinking aloud and just says what he's thinking. It's half reaction, half just
really hoping what he says will get through to them.
As for the trauma part, part of it is just that everyone else has some really severe trauma compared to him, and they never tried to cope with it properly. The sisters continue to laugh and smile because it was their old coping mechanism, and Kurenai's powerful drive to protect Rokurou is because of her guilt over almost killing him as an infant. From what we've seen the people who fall victim to the paintings either try to avoid thinking about the trauma or just incorporate it deep into their psyche. He's the only one who has come to accept that his trauma was part of his past and move on with his life.
On a related note, I think Zanka is a good example of this point. After seeing Deido kill his older sister as kids he went into shock (as any kid would), and by the time he recovered the Sakamaki family had left. Unlike everyone else he didn't go out of his way to avoid it or have that experience become a defining feature of his personality, he simply never had an actual chance to confront it properly. He managed to break free specifically because he WANTED to confront Deido about it. He's the only other person we've seen who wanted to face his trauma directly and get closure.
Overall there are some very interesting psychological themes going on here.