You pull them aside in private and ask if there's a problem. You call them out right then and there. You say something passive-aggressive back. Hold everyone back and wait until there's a definitive winner.
You're a hypocrite who thinks you're the best person who has ever lived, but you're not alone. We're all that way, and it's just fine—so long as you forgive everyone else for the shortcomings we all share. Every one of us feels we are the best person we know, and if you don't believe this you're either lying or there's something wrong with you. Before you go write and angry comment or email let's talk about this for a minute.