If I were an adversary of the US and I needed some information to solve a problem, I might ask a question on Physics Stack-exchange with the goal to get info I'd not get otherwise.
Why do I ask this question? It's human nature for people to "out perform their peers" to get up-votes and be "the one" that gets the status of "public approval". Our adversaries know that Americans are rats for this bait and easily take it.
Has the DoD been aware that people might be using this platform to gain knowledge they might not get otherwise? What measures are taken by Stack-Exchange to prevent escape of sensitive information? Well on second thought, I'm not sure the staff here would know how to detect sensitive information... so there you go.
Why so many downvotes? Where's the Diversity, Equity, and Inclusion? Isn't this question just as valid as others? I feel offended.