Literally an order that Podesta issued to the DNC members also, revealed in the email leak.

https://www.independentsentinel.com/remember-podestas-emails-compare-your-opponent-to-adolf-hitler/

Podesta email #25. In an email “Compare your opponent to Adolf Hitler. This is your heavy artillery, for when your opponent is obviously right, and you are spectacularly wrong. Bring Hitler up subtly. Say, “That sounds suspiciously like something Adolf Hitler might say,” or “You certainly do remind me of Adolf Hitler.”

When the dems reach for the nazi analogies, take that as confirmation that they are 'spectacularly wrong'.