Regarding food pyramid:
Well, it turns out that the food pyramid was heavily lobbied into shape by dairy and meat industry, rather than there being a 'vegetarian agenda' now. Disclosure: I'm not a vegetarian, but I am lactose intolerant.
Regarding presidents and history: well, it's only been 50 years since the civil rights movement, there's a lot of blood in American history that hasn't been addressed, and the descendants of the victims demand recognition - which they simply couldn't do any sooner.
But that issue will haunt most of the nations on earth for a while: that the story of the glorious inception of their nation isn't actually so glorious, that their nation wasn't created by god himself but is historically contingent, etc. Etc....
Coercive relationships with much older men were a thing in the past, and they aren't any more - a good reminder that we should not think we are holding the one universal truth in our hands NOW - as they did in the past.
The problem is obvious: can you ever act on anything you know, or will it appear barbaric in a few centuries from now?
And it's not that everything is wrong now - it just wasn't right to begin with, and there's room now to talk about other views, which there just wasn't before.
There's not just a history of items of knowledge - these items are imbedded into a larger framework of a narrative about the world. This narrative is currently changing, and that's why it seems all the individual items of knowledge are shifting at once.
_________________
I can read facial expressions. I did the test.