There are two issues here, the first being is nudity legal—an issue San Francisco is having to deal with.
The second, I am confused about. Is he saying the sponsors of the Pride event had him arrested? If so, he is wrong—people in control and having responsibility for an event have a duty, morally, and legally, to control it and they have a right to decide who and what is included in the event. If they said no nudity, and he tried to skirt the rule, he is wrong.
He has no right to harm an event for others just to satisfy his ego. Let him plan his own event.