One of the attacks fringe belief enthusiasts (pick your poison, from creationists to conspiracy theorists to cryptozoologists) is that scientists won't overturn old ideas because it would endanger their egos, their grant money, and their jobs. I've heard the notion that astounding archaeological discoveries have been covered up and destroyed for this exact reason (IIRC, referencing all the 19th century reports of giants found in North American graves).
Paleoanthropology shows how absurd this notion is. Now, I'm something of a lay person in this field (my expertise is in Mesoamerican archaeology, early European colonialism, and ceramics). But it's pretty obvious that in the last decade or so, our picture of our hominid legacy has changed dramatically. We've got another species of hominid co-existing with humans right up to edge of the Holocene, in the form of Homo floresiensis. While the floresiensis case is still being investigated to better understand the nature and culture of these little people, the concept of another species of Homo existing so close to the present is fascinating. It now looks likely that Neanderthals did indeed contribute their genetics to modern humans, a long contentious question answered, though the exact nature of the interaction (besides the genetic mixing) with modern humans is still fiercely debated. In the 1990s, symbolic material culture and behavior was generally believed to be something that exploded with new tool technologies 40,000 years ago or so in a triumphalist conquest of the world by modern humans overtaking all the other versions of Homo due to some revolution. Now we know that such behavior is twice as old, wrecking the neat 40K modern package idea. I'm sure there are other earth-shaking discoveries I'm forgetting.
And now, stone tool use has been flung backwards a million years, before the existence of our genus, dramatically changing the picture of Australopithecus.
The story of humanity and its cousins has changed dramatically in only a few short years. And there is every reason to believe it will change even more as new discoveries are made, and new techniques are brought to bear. And yet, no anthropological men in black swept it under the rug, no cabal of status quoticians hid the fossils in Warehouse 23 (not a typo). Scientists like when their discoveries make comfortable ideas fall apart. Not surprisingly, those who accuse them of the opposite are often promoting a new-fangled version of a comfortable idea already blown apart by earlier discoveries.