Facts are fairly easy things (not for the MSM and Republicans, but eh...).
Science deals largely with facts.
Science is hard.
There are two primary reasons for this: lots of required background and complexity of interpretation of results.
As an initial aside: there is a largely philosophical [scientific] notion that facts are not so easy. This has to do at some level with uncertainty, but even beyond that, with the fact that most scientific facts are obtained under the premise that one or many established theories are correct. Scientists, by and large, do not have much of an issue with this, and aside from playing games, there is no reason to call obtained data something other than a fact. So I'll be pretty much ignoring this...
While there is quite a bit of science that is accessible to the masses, it is really mostly old. The latest science, and that which is most impacting our present/future in complex and highly debated fashion, is not. Climate change is a perfect example, and new energy tech is also here. It is difficult because you need to have a strong science background to understand it, and even then, if your background is outside of the area of expertise then you may be hard pressed. For example: I have a conceptual understanding of relativity, but I can not do the general and special relativity corrections necessary for GPS calculations.
Standing on the shoulders of giants sounds easy, but you have to climb up there first. That means education and most of the non-scientist population don't bother. There is a phenomenal amount of science out there. Some is interrelated, some is not, but everything that is happening today in science happens on top of a broad base, that is commonly understood within science but largely ignored outside of it. Let's have a quick look at how this works in energy tech and climate...
In energy tech, most if not all people have heard of solar cells, and most of those people understand that they produce electrical power from [sun]light. Only a very small number--possibly a majority of scientists, though not likely--really understand how they work, however, and only a very small subset of that group really understand the challenges of using solar as a major energy source, and within that group are many pockets working on ways to improve different aspects of solar energy collection who only have detailed knowledge of their own projects and a few others that are related.
...
Global climate history is gathered as detailed in tree rings, ice cores and geologic strata. There is a fair amount of understanding of climate history, but the cause and effect nature, the interrelation between different areas and aspects, and extrapolation to possible futures is an immensely complex problem. It is a problem which scientists have been engaging in and refining only in the past few decades. In large part this part of the work is recent because it was virtually impossible without computers. The nature of development in the field is such that current knowledge and understanding is orders of magnitude better than that of 20+ years ago. Despite this, many naysayers point to research from the 70's as a counter. Research done in the 70's is about as relevant to climate change as research done in the 1800's is to evolution (when Darwin was alive, but before we knew about DNA), that is, it is important, but too much was not yet understood. It could be that 10-30 years from now we will say the same thing about our current understanding, but we have to do with the best we know, and 70's climate research isn't that.
Those couple of examples represent quite a bit of science that is available but not commonly understood, yet they still don't even begin to demonstrate any expertise on either issue. Actual, expert scientific debate is incomprehensible to most and therefore boring and not TV worthy. As such, most of the public science debate in this country is between political pundits and/or crusaders who haven't got the background to be relevant, but who are making the noise and are picked up by the media. Unfortunately, since most of the public is also insufficiently well educated, it sounds to too many like real debate. It isn't.
The other point, and the reason that science is hard is that, even when one has the proper background, is that interpretation of results and extrapolation are not trivial problems. Multiple iterations, many different experimental comparisons are helpful, but even still, general consensus can be hard to come by, especially when multiple scientists are working the same problem from different angles. Ego--not in short supply among top scientists--makes resolving differences harder still.
Differences of opinion bordering on arguments between two scientists who are both terribly well educated and also likely leaders in a field, are not just beyond the understanding of the general public, but often beyond the understanding of the general scientific community. The notion of "teaching the debate" sounds nice, but as a PhD in the field is necessary just to understand the framework on which a scientific debate is held, it really is quite ludicrous. But these differences of opinion occur, and quite regularly.
Science is a constantly growing and shifting body of work and ideas. The generally poor science knowledge of the general public means that much important science has become an article of faith for many. When something is a question of belief rather than fact, then the boundaries become fuzzy and arguments and "ideas" that do not qualify can begin to seem as credible as real science to those who don't understand what science really is.
People believe in DNA because very few have seen or understand the evidence that proves its existence. The good news is that most people still have more faith in science and scientists than they do in financial service employees, or politicians. The bad news is that they have faith and not understanding, and it is being eroded.