Here in the United States, we pride ourselves on our First Amendment rights, including the right too free speech. That means, among other things, that we are able to criticize public figures, especially if opinion is not cloaked as fact. When Americans rebelled in the late 1700's, one thing we wanted to escape was persecution of those questioning those in power.
I strongly support this. He is actually a brave man if he said this. We just have to face the truth no matter what. If a person is making a mistake we have to tell them no matter their status in the society. Therefore, Robert Reich made his point to the president elect.
Yes, it is appropriate to refer to the president-elect as "mean and petty, thin-skinned and vindictive" because he is true. After a few words of mild criticism, Donald Trump took to twitter to disparage a union leader who represents Carrier workers. Since then, this leader has been subject to threats from Trump's acolytes. This is very dangerous.
Mr. Reich is an outspoken progressive and is surely free to give his thoughts and analysis about the incoming Trump Administration. However, he should limit his public pronouncements to analysis. Giving Mr. Trump unsolicited advice as to how to conduct himself does not further Mr. Reich's cause as Mr. Trump is not likely to hear or heed it.