What a pain.

I think if you hadn’t made an effort to speak with this person about his behaviour, and if your empathy hadn’t been so rudely rebuffed, it might have been fair to ask whether he was having problems in his life or if there were other factors at play in his behaviour. His response to you, though, says a lot about him. And whatever is going on, there’s no excuse for spreading nastiness and propagating nonsense.

As you alluded to in your email, it’s one thing to bloviate, another thing to demand people listen to your drivel and another thing entirely to confine your aggressive sanctimony to one group of people.

Your desire to see the back of him is completely understandable, but having him sacked could be tricky unless he’s obviously breaking the law or an organisational policy.

This person is, above all else, an epic bore. If you have the time, inclination and resolve – and most importantly, if you think it’s safe to do so – I would tell him this. Even if it fails to puncture his self-delusion, you’ll at least have got a burning truth off your chest.