Tom,
There's little problem with data, though you only get what you ask so prior assumptions can always play some part, the issues arise in interpretation. Many I know in astronomy (somewhat) and optics in particular try to avoid interpretation as they know that trying to fit it to theoretical doctrine makes nonsense of it. But most others entirely ignore the implications anyway! Better to just publish the findings or describe it as anomalous (or keep it as 'trade secrets').
I tear my hair out with fellow astronomers almost every day reading the on line journals and seeing the nonsensical interpretations some suggest to make things 'fit' with what they believe, or sometimes even with 'new' suggestions.
Mostly they simply don't read a wide enough range of other work to update what they were taught at Uni. Many in research read an exceptionally narrow range so get no perspective or 'cross pollination'. Many seem to read ZERO papers and only update ideas at the odd conference!
It's human nature and the way the brain works to test veracity against prior neural network patterns rather than entirely objectively. I mentioned Hannes Alfen's comment recently, strolling between labs from one bunch desperate to solve some problem to another down the hall on different research who've actually resolved that exact problem. He says how he tried to get them to speak to each other, but even when forcing them they found they spoke different languages!
I've had VERY many similar experiences from undertaking a wide range of courses. It's those invisible blinkers we all have. NONE of us can believe we have them. We all assume it's OTHERS talking nonsense when we can't understand, so make little effort to do so. Perpetuating the lie that we're all objective is what keeps theory in the rut.
It's as little conscious as it is entirely prevalent. Lahav calls it normal theoretical entrenchment.
Back in academia, when asked what could be done to improve science teaching the main request for for 'less change' in the subject. The fact that science is mostly about discovery and advancement seems to have entirely passed them by!
Best wishes
Peter