Most of the massacres alluded to here used some variety of misinformation, secrecy, or euphemism to keep the calm and quell any heroics. Think "relocation" or "re-education". Even in the cases where they knew their fates, the settings were likely too swift or chaotic for any chance of successful resistance and there are countless stories of these attempts.

Frankly, this reeks of victim-blaming and shows a real lack of imagination for what has gone on in the world that you don't know about.