A term for this type of language
You could say that is a veiled insult.
I like "innuendo."
Webster's Definition
Related Words
It's called charientism
derived from a Greek word meaning a figure of speech wherein a taunting expression is softened by a jest, an insult veiled in grace (wiki)
Edit: I just found another earlier reference to this form of Rhetoric: it is also referred to as charientismus.
Also commonly referred to as backhanded complement
Another term for this type of backhanded compliment is asteism
polite and ingenious irony (freedictionary.com)