From 4:28 on wards in this video, I love how he sticks with his point. I'd have stopped after 5:23, but Piers continues to use this point against the bloated American.
That's what one needs to do in an argument. If you feel your point is right, it's not enough just to take the view "oh I'm sure the audience sees my point". If the other party makes an attempt to dismiss your point, I think it's important keep using that argument against over and over unless they refute. In doing so you make them go around in circles, and thus they make a fool of themselves. And in truth the discussion can not develop until an agreement is made on such a point.
Once again at 5:55, just when I would have said to myself "okay that's enough", Piers continues to use his very own reply against him. This is so crucial to arguments. It's amazing the way people don't listen, or deflect. It's got a lot more to do with calling people out on their bull**** than it is to do with knowing your facts.
https://www.youtube.com/watch?v=NsZa4V9T4lg
Also, at 4:07 you can see the guns campaigner itch his ear as he is most likely lying. Though I'm not too sure of that having looked up a list of Australian massacres.