pay a backhanded compliment
pay (one) a backhanded compliment
To insult or negatively criticize one in a manner that is disguised as or seems like a compliment or bit of praise. A: "Those pants really suit you—your legs don't look nearly as fat in them!" B: "Wow, talk about paying someone a backhanded compliment!" It's hard to tell when she's being sarcastic as a joke or when she's really just paying you a backhanded compliment.
pay someone a backhanded complimentand pay someone a left-handed compliment
Fig. to give someone a false compliment that is really an insult or criticism. John said that he had never seen me looking better. I think he was paying me a left-handed compliment. I'd prefer that someone insulted me directly. I hate it when someone pays me a backhanded compliment—unless it's a joke.