I’m thinking that Charming found out Dr. Whale had a one-night stand with Snow/Mary Margaret during the curse.
I agree. Charming might be trying to make up for everyhing that happened to Snow during the curse. I hope this season does have them dealing with the fact that David didn’t believe Mary Margaret when she was accused of murder or at least having Charming trying to get over that. As much as Charming can lash out at Dr Whale for what he did to Snow, he’s also got to deal with the fact that he did his own share of hurting, perhaps even more so than Dr Whale.