Check out the context for yourself. The quote is from Starship Troopers.
It's not that Heinlein doesn't understand or is deliberately obfuscating, he's simply using a perspective different from your own, IMHO. The way I interpret Heinlein here is that rhetoric and flowery prose doesn't *give* us freedom, and that freedom is something that needs to be fought for, to get, and to retain. Read (or re-read) the novel -- I think you might learn something.
I read it during my formative years, and it was influential in the shaping of my political views; but that was so long ago I couldn't tell you what it said or what I liked about it (the politics part - what's not to like about powered armor?). In the given context, it's not a different perspective from my own - it's what I was saying here and elsewhere: that simply recognizing rights doesn't secure them. Out of context, that quote sounds like Heinlein doesn't even believe in the concept of rights inherent to a person, or that it's irrelevant.
What the Declaration states, and what I believe as well, is that these rights are real and exist; whether respected, trodden upon, forgotten, or codified into law; and the moral corollary that everyone has a duty to respect the rights of others; disagreeing with the assertion that rights are arbitrary, not transcendental, and can be revoked by a society. Ultimately it's a philosophical question: what's a "right", how do we get them, and how do they relate to morality in the context of society?