Why do people think we live in a Military Dictatorship?

In so many blog posts (such as this one), I've seen the following line of reasoning...

[Fill in name] was a [fill in military service credentials] in [fill in location of combat experience], so [fill in liberal] need to shut the fuck up, because [fill in liberal] don't know what you are talking about.

Now if they are talking about specific military specialities (combat training, tactics, etc.) then I'm inclined to agree. However, if you are talking about national politics or foreign policy, then you are dead fucking wrong. Why? Allow me to explain in the most simple terms possible.

The United States is a representative democracy in which the civilian branch of the government commands the military, not the other way around. Civilians, not the military, are the in charge of policy. See, it's actually quite simple. If you prefer a country where military service is a prerequisite for shaping policy, perhaps you'd prefer living in China or some nice South American military dictatorship?