This! Tell them you're recording as well...should be enough to keep them from lying on a report. "MOST" people (not all), will realize they're in the wrong and move along. Even better get another witness or two. In this situation, a red coat would be great (jot down names). A few months ago, I had to tell an A line to stop cussing while pax were deplaning. The Captain and another FA were standing right there. I haven't heard anything but would have zero problems explaining the situation.