Technically, you are registered, as you require a DJI account to use the application, and your logs contain any information to back up/confirm your flights. So, in the case of someone confronting, might I suggest that firstly, you ask that they wait for the aircraft to return and land to ensure safety (you are not going to debate when concentrating on flying). Then you can explain that you are registered, a licence is only required for commercial use, although from the 1st October 2019 the UK will (not yet confirmed) be insisting on registering all craft over 250g, and I am in agreement with that, as safety and responsible use is important. "If I am unknowingly standing on private land, I apologise. I am allowed to fly over areas at a specific minimum altitude, and my logs will confirm that. I did not hover, take images other than the aerial landscape as ahead of me. You are welcome to see the footage I have, and I am sorry if you felt you may have been aggrieved, but I can leave and fly somewhere else if it bothers you." Speaking in a non-confrontational tone will help get the message across; you are not wishing to argue with him, and you can even agree that if he had nuisance flyers who had been flying too low or such, then you can understand it is not what the hobby is about. I suspect his lashing out about shooting it down was lashing out, and in that instance would not mention it, simply because it may appear you are going to argue who was in the wrong. (of course he would have been liable to criminal damage had he shot it down).