They say x, ask for where they heard about x. They say from y news organization, ask the source for y. If they say z, if z is actually an actual document or otherwise, ask them where in z does y claim x is true.
If z is just another news organization, keep going until they provide (or don't provide) an actual document. If they can't procure an actual document, send it yourself. If z is just another video cIip, ask them for the whole video. Provide them the entire video if they can't.
Do not try to antagonize. Just simply ask the questions as if you were trying to understand their point of view, to learn something we might not have heard.
More info: After WWII, the Smith-Mundt Act was passed, making it illegal to use false propaganda against the American people. It was ok to do it overseas, but not against Americans at home.
Obama and Congress repealed that provision.
Since then, we have had a steady dose of false propaganda.