The text mentions two legitimate camp sites within a kilometre of each other, perhaps he moved on to one of these in order to use the showers afterwards.
If the farmer had been intending to spread the whole field then I would say it was just the cycle-camper’s bad luck to be there at the wrong place and time but because the farmer deliberately paused to cover the cycle-camper and his possessions before leaving again it could be considered to be a form of assault. That said, as a landowner my sympathy lies with the farmer. It seems like a gross overreaction but you must consider the cumulative effect of the same thing happening week after week, verbal abuse, cleaning up after litter louts, broken glass, animals allowed to stray… it wears you down to the point where it’s easy to get things out of perspective. You cannot take any one incident in isolation, there is a cumulative effect of the intrusion and abuse that we face in the countryside…it adds insult to injury to have someone standing in your garden yelling “right to roam” in your face (and I do mean my actual garden, they were looking in through my kitchen window as I made my first coffee of the day)