Prevention https://theboardmeeting.blog/how-do-you-keep-up-with-trends-in-your-industry is the best way to deal with difficult board members. Make sure your agency's objectives for board members are clear and they are able to align their vision with the organization. This reduces the number of situations where a board member's advice can be counterproductive. However, if a problem occurs take action immediately and do not ignore poor behavior. Delaying will only make it worse.

Direct intervention is the initial step - a meeting one-on-one with the person in the middle of trouble. Be professional and calm but also clear and communicate your concerns clearly. The ideal scenario is that the person will agree with you and change their behavior, however should that not work, consider stepping up to group intervention with the chair and/or anyone else who the board member is highly respected by. You may want to review your agency's Values statement and/or other documents that govern the organization for words that could serve as a standard for acceptable behavior, such as treating people with respect.

Another alternative is to request the person to quit the board (ideally in a voluntary manner but, if necessary you can do it through a vote in confidence). This will require some careful preparation and planning prior to the meeting or conversation. For instance, make sure you know the key issues you'd like to address and have an elaborate response ready. Be assertive, but keep the appropriate tone.