This is not an answer about source materials. This is a response to the question itself.
Yes, philosophers do have a duty to question their government. As do auto mechanics, teachers, plumbers, and software engineers. Every citizen needs to question their government; and if the government starts to stray from the good; then the people need to speak out. Surely we who remember the twentieth century have seen what happens when the people shirk their responsibility.
“It is the first responsibility of every citizen to question authority.”
-- Benjamin Franklin
Do philosophers have a special duty, or any particular duty by virtue of being philosophers? No. Why should they? Philosophy is a profession like any other. Is a philosopher presumed to be wiser than others? Not in contemporary society by any means. A professor of philosophy writes books and studies other philosophers and can tell you what each one said.
So if you ask a philosopher, "Should I put my suffering loved one out of their misery?" a philosopher can say, "Well, Aristotle said this and Russell said that." But they can't tell you what to do. They are not wise men. Just learned ones.
I see no connection between that occupation and any special rights or obligations in society. We license doctors and we license plumbers. But we do not license philosophers.
[Of course we do license professors of philosophy. But that is not the same thing.]
Every single person in society has an obligation to question his or her government; and to speak out as needed, according to their own conscience.
Everyone has a conscience, not just those who can quote Aristotle. What makes anyone think philosophers are special? And who thinks that, besides the philosophers?