A stile'd be a good idea - but that'd encourage others to dare walk on this land. Not what the chap wants by the sound of it. Personally, I wouldn't give a toss whether he told me to "Keep Out" or not - I'd still look at it if I wanted to.
But this seems odd: how come we've had 3 complaints from land-owners to TMA about 3 sites in the last few weeks. Is some tosser from some other website, or some miserable researcher, trying to discredit things here, or am I just being paranoid...? Or are are they truly miserable "incomers" who've moved up here with the wrong attitude. Makes y' wonder.