Next time you're setting up, or helping to set up, a townhall meeting, and you've been warned weeks in advance of a strategy by the opposition to shout you down, here's what you do:
Get a projector. You don't have to buy one, you could borrow one from a friend. More than likely, there's a light-colored wall on one side of the meeting room you can use as a screen.
Put together a presentation (if you don't have PowerPoint or Keynote, you can use the free Google Docs presentation tool) with each of your important points you want to get across. I would also include easy-to-read sources where I got my facts from. Go through each slide one at a time. Don't use more than three bullet points per slide. Go through the entire presentation at least once. Build it so that it doesn't require you to say anything.
If someone actually manages to make a question heard, you can always go back to the slide that answers that question. You might, in the case of a crazy person, include a slide like "Your question is based on a false premise, and I'd love to know where you're getting your news, because they are gleefully lying to you."
I'm ashamed I didn't think of this earlier, but then again, I only think about public policy for a few minutes a day.