Please read the article. He refused to leave a scheduled meeting until the Board agreed to allow his son to be excluded from certain classes. There is no legitimate reason for such a meeting not to be public, in this case. Why on earth would the school officials insist that he leave without this agreement? Why on earth would they call the police?
Haven't you heard of civil disobedience?
Please read the article.
His action to remain might have been civil disobedience. One thing that implies is violating a rule or law to protest. However, if you do, you have to be willing to suffer the consequences. People who demonstrate and break a law need to be willing to live with the result of their action. The most common role model was MLK. He didn't whine about going to jail. He knew it was part of the deal.