Science is not all fact. In fact the majority of it is theory. What they call fact is simply what they could not disprove given the current information available through experimentation. But, the science can be corrupted if money or ego gets in the way.
Ego: There are a number of scientists who want fame and the fortune that comes with it. This was most certainly the case in the earliest days of the scientific community as they searched for the missing link between man and monkeys. So much so that these so called scientists made fake skulls and even fake bodies that would only later be disproven through advances in science and technology. We also have a similar issue today. The scientists who said dinosaurs may have had feathers were at first vilified. It would only be later that his ideas would be accepted by the overall scientific community. However, a new issue has arisen. Now that the feathered dinosaur idea is accepted the scientific community rejects any counter argument to the idea. As such, scientists who present evidence to the contrary are now being vilified instead. All this pertains to ego, as the pride of these scientists gets in the way of questioning how our natural world works.
Money: Money is also another motivator for corrupt science. A great example is the global warming/climate change debate. Many in the media will quote statistics that the earths temperatures have risen 7, 20 or even 30 degrees within the last 100 years. One problem, within the last 100 years the earths temperature has only increased by 1.2 degrees according to climatologists. If you also look at the whole ice sheet melting you will discover that during the winter it completely recovers only to melt again. As to why the water is possibly warmer is still in question however. But what about the polar bears you ask? Well the truth is polar bears while listed as endangered have never sunk to a level that would classify them as an actual endangered species. In fact their numbers are only growing. So why all this misinformation? Well it is because government pays for the research on global warming. These scientists are being paid to prove something rather than seek the truth. So they fudge the numbers so as to "prove" what the government wants. These scientists know that if they contradict the people giving them money then they will loose their funding and thus be left without a sponsor for not just their research, but their lively hood.
Another example is the debate over what’s better to raise a child. Are gay couples, single parents or traditional families better able to raise a child? Well it depends again on who provides the funding. Usually I see gay advocates who fund studies on gay couples having the gay couple coming out on top or equal to that of the traditional couple. Likewise those who fund studies on single parents, or traditional couples have there group come out on top. So its not about proving who really is better at raising children, its about the funding these scientists are getting as there results are used to support the "dog and pony" shows put on by these advocacy groups.
Conclusion: Ego and money are the primary movers and shakers of science and are what obstruct the pursuit of the truth. Coercion and ideology also play a role as well, but from my perspective do so at a much lesser extent. So if someone says this is fact, make sure that the fact comes with legitimate information to back it up.