How do we resolve subtle intimidation over time?

Security cameras? 

Security cameras?
-@stumpy

Yes.

That would sort it out quickly .. and make great evidence for the police

I take it you're not living permanently at the property, and this is going on in your absence. A VERY old French story, I'm afraid. Had an English boss in the same boat via a vis her country property 25 years ago. The security cameras are an EXCELLENT idea,and probs your only option at this stage. Pretty cheap here in France and easy to install.

Interesting to hear it happens to others. My British/American family had properties in France for many decades, mostly renovated or built from scratch on land. At one point I inherited a country property but did not have time to return to France to renovate and sell it for a while. I had already had reports it had been broken into and vandalised, so I flew over. The town and the people wanted to buy it for 1/4 of its worth (the other properties were already sold and became state owned). They bullied and threatened me and kept vandalising the property. One day the front gate was destroyed - I was told a car rammed into it. The behaviour was so bad and frightening I was determined to sell the house to a private buyer and I did.

Good on you! Never give in to local bullying. While this sort of intimidatory behaviour, in France, is recognisable to me and others in this thread, I'm sure it happens in other European countries,particularly if you happen to be an English speaker ( thanks,Empire!) However,I'm equally sure that largely empty,desirable properties in Australia would be subject to the same unwelcome attention if it was known they were owned by " that rich bloke from overseas". One of the many problems besetting an absentee landlord/ owner I'm afraid. However, don't cave in,and sell it for your price,not theirs. Good for you.