Both the police and the reporters were calm and polite. The police told them they had to clear the street and instead of obeying the order they asked to let them know when they were going to actually walk down the street. Since they refused to obey the order they were detained and escorted out of the way.
Being a reporter does not give you a free pass to disobey orders, specially during situations like that. Being a police offer also does not give you the right to mistreat people of course, but in this video everyone actually behaved very well.
Police officers don't have carte blanche to issue orders and force people to comply. We're a nation of laws (supposedly). They were asked to move and they understandably wanted to know where they should move. Then they were arrested.