From what I see posted here, we don't need to YouTube it. You're preaching to the choir here @Aspychata, lol.
But what do you do when someone is lying to you? Do you
a) Call them out on it?
b) cut them out of your life without explanation?
c) smile right back and pretend you're stupid?
d) other?
It depends a lot... it depends if you've got material evidences or not, it depends the type of person, situation, relationship, what it would imply for you, what is the matter, the repercussions it has, if it's really beneficial to handle the situation or let it pass and move on, ... it's a big subject I think...