There's a whole interesting physiology behind learned helplessness (of which this is a minor variation).
In its defense, there's some practicality to it; we wouldn't say that a "get out of debt" plan that involved spending all available money on lottery tickets is worthwhile because "its not gonna happen". But defeatism is just a shortcut to say "I don't want to talk/think about it" in many cases.
And in this one, if the US Gov't required that all routers purchased by any agency they could influence had the ability to run open source code it would certainly shake up the market.
Why? You'd need to get someone electorally useful involved. That, unfortunately, elimiates a lot of the nihilistic, holier-than-thou tech types. But that's pretty doable nowadays. You just need an electorally-relevant group of people on your side.