I find this attitude disgusting. There should be a law against the government purposefully lying to us for propaganda purposes, no matter how good the cause might be.
Looking at the government as monolithic and omniscient, sure. But its the same as any organization: made up of tons of people who don't all know everything, who disagree with each other about things, while generally trying to do the right thing. And sometimes they get it wrong (I too remember the food pyramid)
Sure but you are assuming the government or our representatives (or even you yourself) know what the truth even is in order to lie about it.