I'm reluctant to accept the caricature of evil dictators who have a "kill now" button on their desk for anyone who tells them something they don't like. I don't believe anything could get done that way in the real world.
Certainly the census you're referring to is a sad example of political denial, but it doesn't say anyone was killed (just imprisoned, and while prison isn't a lot of fun, it's a far cry from execution) and my guess would be that the article glosses over a lot of detail, like meetings with Stalin where he said "Hmm, I don't think these results are gonna work, they're very politically inconvenient and must not represent reality. Fix it. Let me know if you can't, and I'll find someone who can." The statisticians failed to "fix" it and failed to inform Stalin that he needed to find someone else to conduct the manipulation he sought.
I understand that statisticians with integrity would decline the responsibility to change the numbers (though statisticians with a sense of self-preservation would resign rather than release accurate details), but numbers on paper are a much different ballgame than "this structure will literally fall apart and kill millions of people when it does".
Reports and studies are manipulated to fit an agenda constantly because they're so easy to manipulate. This happens all the time now and surely it happened all the time in the past. The nice thing about construction is that you can't manipulate the outcome. Something either stands or it doesn't, regardless of human opinion, threats, or insistence.