I would say that the PM needs to do the best for the company, which sometimes is defending their team, but others is making their team understand a recent company pivot/shift.

A PM without the support of his team is dead. But if he doesn't get along with management, he and his team are also dead.

Yes I totally agree with you. For clarity when I said "defending their team" I didn't necessarily mean act as a representative to argue their views to management. I've seen many times when what a team wanted would have been really bad for business, which in the end serves nobody.

In one case I actually saw a great engineer destroy his company by basically doing what he wanted to do rather than what management wanted. He was so irreplaceable that they had little choice but to allow it. In the end he turned the codebase into a nightmare of half-baked untested crap that not even he wanted to work on it. That has stuck in my mind for years as something I want to avoid.