Many Creationists have argued that scientists would not accept any evidence against the Theory of Evolution. There are some claims that this has already happened, and that the evidence has been ignored or even suppressed.
Obviously, scientists are human. Egotism, embarrassment or greed might cause one person to try to hide something. It's happened. However, history shows that the process of science is extremely good at detecting and correcting such problems.
To outsiders, the scientific world might seem monolithic. But inside, there are factions and even feuds. Funding is always in short supply, so groups compete. They get to see their competitor's scientific proposals, and they have incentive to point out flaws in the other group's proposal. Similarly, groups spend money, and they have to show their sponsor that they received value. For example, radioactive dating is usually done by dating specialists, and the scientists who use those services are free to switch to someone else. So, dating labs compete. For example, a funding agency might send bits of one single rock to many dating labs, and then publish the results if they didn't all get the same answer. If a technique (or a person) isn't reliable, then scientists want to know that. They don't want to blow their budget on the wrong thing.
Even worse, much of the funding comes from the government, and it may be a crime to misuse such funds. Suspected scientific misconduct has actually resulted in congressional hearings. Also, federally funded work must comply with numerous regulations that forbid things (like work with fetal tissue) or that require reports. None of this is taken lightly, so there is a lot of "due diligence".
On the larger scale, branches of science have to argue that they are worth funding. From 1935 to 1965, spectroscopy wasn't funded much, and then there was a big upswing after lasers were invented. The losers in these funding battles don't take it lying down. If radioactive dating didn't work, then that would be pointed out - perhaps by the weather bureau, or perhaps by cancer researchers. When the money comes from just one big pot, winners can get scrutinized by a whole lot of people. And evolution, as it happens, touches on a great many sciences.
On an even larger scale, science is international. During the Cold War, Russian and Chinese scientists would have loved to expose American scientific failings, and vice versa. And there are scientists of almost every religion. I can't image all the Hindu, Moslem and Buddhist scientists putting up with any Christian or atheist agenda.
Graduate students have no investment in the status quo, and dream of acquiring an overnight reputation by overturning some orthodoxy. My niece pointed out a flaw in someone else's published data. History shows that students are very willing to overturn old theories. Science switched to relativity, to quantum theory, to particle physics, to the Big Bang, and to evolution largely because students were won over by the evidence. In each of those cases, the new theory was attacked vigorously by the old guard. Those theories are with us now because those attacks failed.
And finally, scientists have a tradition of admitting their own failures. Retractions happen - for example, Nebraska Man was retracted.
So, whenever someone tells me about evolutionists suppressing evidence, my first reaction is that they're talking about some other world - not this one.