To clarify, what were the previous posters being dishonest about? The threat of the boiling water? If it’s that, I would conjecture that the cop mishandling the situation was what made the threat even a little credible.
If not that, can you give me more detail on what the others were being dishonest about?
I think the easiest way to prove he didn’t is to prove someone else did. I don’t think he will be able to do that easily, particularly because I think he made those posts.