That would mean that everything known is a fact...

This is incorrect. Knowledge =/= Fact (it is possible to have non-factual knowledge).

...and that everyone knows all the facts.

This is partially correct. Facts must be empirically verifiable and or logically necessary (Facts must be "knowable").

This does not mean that "everyone" is necessarily aware of every Fact.

That'd be a kill joy for teachable moments.

I disagree. There appears to be a virtually unlimited supply of commonly held misconceptions.