At the risk of stating the blindingly obvious - and I'm sure Decker was just making a joke - but if someone shouts at you and calls you nasty names, then I'm sure you don't really have much of a claim for defamation if you film them doing it and then upload that film onto a website! I think the courts would think you're defaming yourself

But I doubt he is interested in a defamation claim against his neighbours, so filming them is actually a good idea.