He’s been manipulated. As a social worker, this man is in a position of trust, and he has betrayed that trust.
I still think Jack Crawford now is willing to believe that Hannibal is the Ripper.
And his chat with Will during the fishing scene was a hint on how they are working together to lure Hannibal out.
"Dark Will", as it goes in the fandom, is actually being built up by them to lure Hannibal out. And here, Jack’s dismisal of Will’s opinion is more calculated than sincere.
But that’s just me, obviously.
Because for some reason this whole Dark-Will-TradeMark thing rings weird to me. Hey, Will was already plenty dark before, no trope necessary. I’d actually enjoy it more if he is consciously acting up the dark part, based on his always-have-been-there vicious impulses.
I don’t know, I am very conflicted about Will right now, but it’s an issue of interpretation.