Scientists Finally Got Americans to Worry About the Climate

To start with, most of science is not based purely on observation. Scientists will change things, to see if a change makes a difference.

Second, there's no such thing as "unbiased", and it would be unethical to do so. We could run experiments to deliberately infect prisoners with rabies and let the disease take it course.

That's unbiased science, but (we now agree) deeply immoral, to the point that we do not allow this sort of science to be carried out.

Third, nothing about being a scientist requires that people give up their humanity. If a medical doctor walking down the street sees someone choking, that doctor is likely to help. If a structural engineer sees signs that a structure is about to collapse, that engineer is likely to sound the alarm.

Sure, in these examples it's not "part of [their] job" to do so ... but neither was it part of Einstein's job to co-author a letter to FDR warning about German nuclear weapons, nor was it specifically part of Sagan's job to get people to worry about nuclear winter, as a consequence of nuclear war.

And no one seriously says that their political and cultural activism was contrary to being a scientist.

Lastly, scientists are part of a culture. Where do you think the funding comes from? If an organization wants to develop methods to help improve crop yields in the third world, as a way to reduce hunger, then that's political and cultural activism. If they then pay agronomists to do the related science, the yes, political and cultural activism was part of Norman Borlaug's job. He got the Nobel Prize too.