Dear Mary: After we refused a shareholder’s request to install a working fireplace in his unit, he’s been waging war against our co-op board. In a constant stream of social media posts and emails to other shareholders, he criticizes everything the board does — or doesn’t do. He lies about our actions and motives, accuses us of neglect and makes ugly personal attacks. As a board, we’re torn between ignoring him and setting the record straight each time he posts. We’re so stressed over this. Any tips?   Read the Q&A…………………………………..