The problem with this thinking is that the US government regularly engages in actual conspiracies, which the public only finds out about much later. COINTELPRO, MKULTRA, the Tuskegee experiments, Operation Paperclip, the list goes on [1].

So, while it's true that the overwhelming majority of conspiracy theories are dumb nonsense, it remains unwise to dismiss a theory just because it is a "conspiracy theory".

[1] This is almost certainly true of other governments as well! I'm just less informed there.