It's amazing, and disheartening, that the officers and fellow soldiers who threatened this guy are fighting for a Constitution they don't remotely understand. What the First Amendment prohibits is government attempts to shape, control or sanction our ideas (and our expressions thereof). Clearly, however, some people are threatened by any form of "freedom" that does not produce conformity.
As Thomas Jefferson explained in his Notes on the State of Virginia:
The rights of [religious] conscience we never submitted, we could not submit.... Subject opinion to coercion: whom will you make your inquisitors? Fallible men; men governed by bad passions, by private as well as public reasons. And why subject it to coercion? To produce uniformity. But is uniformity of opinion desirable? No more than of face and stature.