I'm not saying he's a coward, but I never undestood those who think he shows any bravery.
He knows very well, of course, that for all his talk about the "opression", "silencing of criticism", "totalitarianism" and so on in the USA and the west, there is absolutely no danger of him being arrested, exiled, killed, or even slightly inconvenienced for stating his views, no matter how distatsteful. In addition, being a tenured professor, he doesn't even take the risk of losing his job due to the dislike of his co-workers.
So his "brave" anti-USA, pro-whomever-is-the-USA-enemy stand, is just a show, a circus act of sorts. It's a pretend fight, where Chomsky pretends to be "fighting" the powers of evil and opression (as he describes them), knowing full well those powers will do absolutely nothing in retaliation. He is no more "brave" than the actor playing an action hero is "brave" for pretending to fight a dozen people at once.