I can only relate what happened to me a few years back. I had an apple tree that was growing at a slant, so I tied some string to it, then tied it to a nearby fence post - only tied, nothing permanent.
To cut a long story short, it was the neighbours fence, and he objected - it was not noticable on his side in any way, but he objected, and removed the string. I thought it was just falling off at first, then I caught him, so I asked him (nicely) to leave it as it was only there to help straighten the tree. He said if I did it again, he'd get the police.
Well I laughed, not only at the suggestion but that he felt it was a matter for the police, but guess what, he did, and I ended up with a caution because of it, and told - officially - don't do it again.
So I guess if he can do that for a bit of string, you can do the same for actually trying to damage the fence.