Have you actually tried talking with him and tried to understand him? From experience some blokes can be confrontational on the trails, particularly in a group situation.
It's easy for us to forget that the countryside is a place of work for many, they don't see it as a playground. The point made about countryside thefts of machinery etc is a good one.
Non-riders do not understand why anyone would want to ride a bike in the dark. Why not explain to him that it's fun. Perhaps it is his livestock he is concerned about, particularly if they need to be moved, or are pregnant, or are youngsters. Talk with him.
As mentioned earlier, I did have "discussions" with a landowner cos I objected to his two Great Dane pups continually jumping up at my wheels and him not keeping them under control on a bridleway that ran through his land.
He ranted then turned his back on me (I was on my own) but I had a long discussion with his wife explaining how frightening their behaviour was. Eventually it came out that they disliked mountain bikers and a mountain biker had even kicked their dogs! What a surprise!
This person was known to some of the Chiltern locals on here. I eventually reported him to the Rights of Way Officer and he now seems to have disappeared.