Wait Just a Minute While I Pull This Knife Out of My Back....

Machiavellian back stabbers, I don't want to sink to their level.  Now that I know, do I want them to know that I know?  Should I make them as uncomfortable as I can, or do I pretend I don't know?  Do I confront them and make them ashamed?  Ashamed for their cowardice?   Ashamed for their slipperiness?  Are they insecure?  Do they see me as a threat?  How do I interact with them in a cordial way now that I know; I can't be fake nice.  That disgusts me.  Can I stop it if I confront them?  Can I prevent it by using punishment as a conditioner?  If I ignore it all together, am I in any danger?  Must I sink to their level?  Am I weak for not?