I think calling it deeply ignorant might be a bit harsh. It's a pretty common misconception, and it does intuitively seem like duck and cover would not protect against the most powerful weapon in human history.
You're right. That was an uncalled for. I'll leave the comment there for continuity, but apologies to the parent poster.
Oh, I'm not dismissive of it helping with avoiding debris falling on your head and perhaps the blinding flash. The issue is the world ending shortly after that due to world war 3.
Would you mind sharing some of your knowledge about it?