Would you have hidden it?

I hope so. It was the right decision in hindsight, since the Nazi nuclear weapons program shut down when the Allies, at cost of some civilian lives, destroyed their source of deuterium. If they'd known they could've used purified graphite... well, they probably still wouldn't have gotten nuclear weapons in this Everett branch but they might have somewhere else.

Before 2001 I would probably have been on Fermi's side, but that's when I still believed deep down that no true harm could come to someone who was only faithfully trying to do science. (I.e. supervised universe thinking.)