If the accounts given are true, IMO it is beyond the Security Guard's job to remove umbrellas, harass beachgoers, etc. Their job is to protect the safety and property of the Westin and its guests. If they feel someone is trespassing, they should call the police to deal with it since that is a criminal matter. I doubt the Westin would want to involve the police, though, since they can't prevent use of the beach.