Ah, neighbours. Bless them - they keep our "people skills" from getting rusty.
Mr. Toad, my guess is that the far neighbour doesn't like your immediate neighbour's trailer any more than he likes your Airstream. He is just using yours as an indirect means of letting your immediate neighbour know that he disapproves of parked trailers in general, given that they have known each other for years and a direct approach may not be in his nature.
If you are complying with the bylaws, party on and try to ignore the far neighbour's distress over the parked trailers. Thankfully, it seems like the ear he will bend won't be yours, but you may want to do something nice for your immediate neighbour for taking the flak.