Well, in that context I think the "Absurd Truth" is referring to certain societal conventions in life we simply accept without questioning, even though they might be completely irrational behaviours.
Comedians are very observant individuals, they have the ability to see past the accepted reality of what is around us, and cut to the truth of it.
Sometimes the absurdity is simply highlighted by looking at a certain accepted truth in a different context, so you see it in a different way.
So a particular truth seems absurd, and thus funny and you laugh.
OR you yourself and your own truths seems absurd, and you might feel embarrassed (hence the fear).
