You can NEVER put too much importance on objectivity and professionalism. To me, these values promote honesty, accountability, and transparency. They also ward off sloppy work, manipulation, and let's face it, straight up lying. If the leader of a research group or an organization stresses objectivity and solid work at all costs, he is setting the right tone for his staff and I believe this research group/organization WILL get respect and become a trusted source of information.
When you gain a reputation for being unbiased and objective, people listen to you. Even people that would normally disagree with your conclusions. These people will listen to you as well because they know you have a reputation for carrying out non-biased work and only go where the facts/stats/evidence take you. You don't cherry-pick your results and you don't skew or manipulate the data that you DO find. I believe this also applies to news organizations that report the facts and do their homework. They don't try to persuade you in one direction or another. They present the info in the most responsible and honest manner possible.
Having said all that, you ABSOLUTELY must acknowledge the fact that those outside the organization or research group ARE biased, subjective, have agendas, are emotional, and will use underhanded and manipulative methods to push their agenda. But I don't think this should stop you from continuing doing your work and striving for objectivity and the proper interpretation of the facts. You simply need to realize the context you are working in and be on your guard at all times. You have to constantly fact check and call people out whenever they are being manipulative or trying to lie. You can't control the underhanded methods and strategies of everyone else but you can certainly bring attention to them whenever you can and continue making yourself more credible in the process.
Of course all of this is the ideal version of how things should happen and there are gray areas EVERYWHERE. For instance, do I have an agenda because I think we should live in an environmentally sustainable and conscious manner? Am I biased for supporting environmentally safe decisions and environmental regulations at the expense of businesses and deregulation? Perhaps, BUT, if you gave me a case and told me to analyze and research it properly, I would NOT let my biases cloud my work.
For instance, I am a proponent of increasing the amount of energy we get from solar. My boss gives me the task of analyzing how expensive it would be for a project to get its energy from solar instead of traditional sources like natural gas or coal. He then asks me to compare the costs and present the info. I would NEVER try to "massage" the numbers or use favorable statistical parameters that push MY agenda on the matter. If solar comes way behind in terms of cost, I wouldn't go back to try to manipulate the numbers and "bend" the truth in any way. I would present my analysis and be as professional and objective as possible.
Of course I would still add some commentary in there on how the negative environmental effects of coal and natural gas are NOT factored in because we haven't placed a price tag on them. I would point out that this skews the calculation and that natural gas/coal COULD be more expensive if you put a price tag on pollution. But, my original analysis will remain intact and I wouldn't pull "pollution cost" estimates out of thin air and put huge price tags on them. If such estimates exist, I would try to find data on them and incorporate them in the calculation.
Here is an example of an analysis gone wrong. Consider a criticism of the California High Speed Rail Authority. In one of their reports, they heavily overestimated their numbers of ridership projection for the train. The data was slim on how many people would ride the high speed rail and they basically cherry-picked outliers that supported high speed rail. I believe this is an example of irresponsible analysis. Transportation experts called them out on their mistake and in the process the High Speed Rail staff lost respect and tainted their reputation for doing irresponsible work. They now have to redo the numbers to gain back credibility and respect. If you think about it, did the staff "lie" in this situation? I don't think they did. But, they were certainly being dishonest and manipulative because as any statistician knows, you CANNOT use outliers to make major conclusions. You are using the exception and making broad generalizations. This is not proper work.
Either way, I think ultimately you CAN have policy preferences and "agendas" such as supporting green buildings, public transportation, and renewable energy. But, as I outlined in my example above, you must ALWAYS be as objective and professional as possible or else people will quickly label you as biased, having an agenda, and presenting untrustworthy info. If this happens, you have basically shot yourself in the foot and you will have limited success in creating change in areas you care about.