I'm not gonna argue the law -- he certainly owns the lake and lakeshore, and it was the lakefront owners who fell down. Yet I'd think a Judge could reach out and condemn his property at a very fair market value for the sake of peace. I understand that law in such cases varies considerably state to state.
But let me make some suggestions to the owners, beyond the obvious legal and politcal ones.
Tree branches fall on fences every rainstorm. Fence posts rot when in wet soil, and fall into gullies. As the bad neighbor planted his extort-a-fence, the lakefront owners can re-landscape to make his fance a high-$$$-maintenence item.
And if the owner expects $30K, why then the county appraisers should re-appraise the property so the lake's tax burden is true to the owner's wishes of its value. I'd say that lake is worth $210K, easily!