My 14 year old smudged a fence and a neighbour is treatening to sue! Is this unreasonable.?

My 14 year old son smudged a neighbours fence, with no more than one or two finger print smudges on the panels, the neighbour has replaced his fence and wants to charge us for 6 panels and is threatening to sue. He smudged it wiping tar off his hands, tar that the neighbour placed over a tree on common ground that my son and a friend were attempting to climb... I inspected the damage and was bewildered as to why this man replaced his fence, he is really being unreasonable and has exaggerated the damage (one panel has a mark the size of a pea which he replaced) please advise! (My son did apologise)