And here we go, the same threatening copy-pasta which he sent to dozens of people over the years, and icing on the cake, the usual report to British police services who are sick of him and his (monthly? weekly?) reports about, well, anyone.
That's what happens to anyone to gets in contact with him, whatever the approach is. Those who try to be nice: it will just take a bit longer but you'll end up in the same situation. So yes, ban him if he doesn't unsuscribe as he says he would (but if you count on that: he almost never does it and anyway he always comes back).