Where would you draw the line? Mostly true? Some true? Mostly false? 100% false? What if there are facts surface later and this changes the truthiness?
Yes, a grey zone exists. That's not a reason for inaction in other cases. Where to draw the line between murder, manslaughter and unfortunate accident ? Where to draw the line between fair use and piracy ?
If anything, start with policing obvious falsehoods ("Obama and FEMA will take all your guns").