Praise to the undeserving is severe satire.
Sarcasm is the lowest form of humor but the highest form of flattery.
A flatterer never seems absurd: The flatter'd always takes his word.
If any man flatters me, I'll flatter him again; tho' he were my best Friend.
Approve not of him who commends all you say.
The same man cannot be both Friend and Flatterer.