I always chuckle when scientists are portrayed as cold, calculating, and heartless, when the truth is that they're more committed to understanding their world than anyone else. Science is a labor of passion, and scientists dig deeply into the inner workings of their world.
So when someone says we don't care about something, just because we have a more analytical view of how it works, I get angry.
But, with passion must come temperance.
As scientists we are positioned to understand how the world works, but that is not all of science. Unless your discoveries are communicated to society, they mean nothing. It is up to everyone who does science to make sure they disseminate their knowledge to the rest of the world.
So what happens when your knowledge is loaded with the political baggage that is fundamentally and irreversibly associated with conservation biology (my field)? Do you trust the data of climatologists more if they're active advocates of fighting global warming? On the flip side, do you trust a climatologist who says global warming isn't happening? Can biased observers give unbiased data?
The answer is yes, but with caveats. An ecologist who's ravenously opposed to Alaskan oil drilling is going to be biased in the same way that someone well paid by a pharmaceutical company is biased. They may be totally objective, doing good, robust science, or they may not, but I would approach either data set with the same level of skepticism and caution. And a policymaker, not well versed in scientific literature, would probably be more skeptical (or less if they agree with the researcher) than I.
So there's a delicate line that must be tread.
So how can a scientist be an advocate? He or she can be an advocate of "science." Our duty is to make sure people have access to information, can analyze and interpret it for themselves, and are equipped to make those management decisions. Without the predictive power of unbiased, objective science, we can't anticipate problems and search for solutions until it is too late.