Different

What would happen if we suddenly appreciate a piece of truth that contradicts with the common belief?

It could be anything, depending when and where you are. The Earth is moving around the Sun, The Garden of Eden is a figurative existence, China was a colony of (forgive my language) barbarians much of the time in the past 800 years (not sure the tense of this clause is correct), or, most recently, democracy is a basic human right. These views may not be correct; many a time it depends on your point of view and there is no absolute right or wrong. (As a matter of fact, the Earth does not simply move around the Sun; both of them move around the Milky Way galaxy.) Nonetheless, your life becomes difficult when everyone believe in one way and you think of the other.

You become a vermin - the gigantic monster that Gregor Samsa turned into.

PS. Of course, many bugs do not have a bad feeling. As Jonathan Davis says,
You laugh at me because I'm different, 
I laugh at you because you're all the same.