Graves knows that Credence is an innocent victim in all of this, that he has been taken advantage of by one of the darkest wizards to ever live. Unfortunately human beings are not always rational and the ones who went through recent trauma even doubly so. And there is this voice screaming at him that without Credence Grindelwald would never come to NY, without Credence Graves wouldn't be kidnapped and tortured etc. And maybe Graves knows he is being unfair and doesn't try to actively hurt Credence. Maybe he just refuses to see him when the young man ask to see him (asking for which really took a lot out of Credence). Maybe Credence overhears something.

Graves is dealing with some issues and Graves/Credence reunion is not exactly all roses. Would like a happy ending through.