Trying to be a bird
If you get curious enough, the collection Expanded Universe contains most of his nonfiction essays, where he tells the reader his worldview point-blank as a matter of persuasion. If you want to go further, there's Grumbles From The Grave, which is a collection of excerpt of letters, personal correspondence, and notes on his books.I have to couch all of this in that, to be honest, I have no flipping clue what his worldview actually was, and its probably a fool's errand to try to glean it from his books because of his writing style. He presumably say, wrote characters he didn't agree with occasionally. But what I do know of it suggests that Vietnam would've been a lot more threatening to his worldview in a way that no other conflict the U.S. had been in... in its history, much less his lifetime, could've been.
So, allow me to quote - first from an article, "Where To?", he wrote in 1950, and revisited twice in 1965 and 1980 where he attempted to predict possible things that might happen in the future (with it being noted that such predictions ain't worth much). I'll spoiler it, because this is a lengthy quotation: I'll underline the most relevant bit and let's all laugh at it in the light of Iraq:
So, while not exactly supportive of the Vietnam war, certainly a worldview more concerned with realpolitik and the reputation of the United States than peace at all costs.
A second quote, about Starship Troopers itself, posted as an afterword to the reprint of an advertisement published called "Who Are the Heirs of Patrick Henry?", itself a response to a movement to have the United States end nuclear testing (without establishing some sort of international force to ensure both the US and the USSR abided by the treaty) addressing critics of the book. Again, death of the author and all that, but might as well let the fellow explain himself. I've snipped a few passages out to keep this fair-use-y and short.
He then proposes a number of other ways one might do this, obviously more as thought experiments than practical suggestions: the government outright selling franchises as a primary means of income, being required to solve a randomly generated quadratic equation before being permitted to vote (with no lower age limit), denying the franchise to males and making it exclusively women-only for a while on the theory women are more practical than men.
Now, there's no shortage of flaws one can poke there, not the least being that racism is a thing and poll taxes and 'literacy tests' and everything else have long histories of being used to deny the vote to a class of people, all the way to the voter ID laws of today. But I don't believe Heinlein is spinning such possibilities out of hidden bigoted motives, and he was not completely ignorant of the realities of politics, having participated in political campaigns himself. I might fault him for being naive, but that kind of naiveity was more forgivable even in the 1960s than I'd find it today. But I think it's clear he is both much more pro-military than the average progressive is today, but that his image of the military was formed from the first and second World Wars, and reinforced by the Cold War. A Heinlein who lived long enough to see the wars of later on might be one of the solid establishment sorts that voted for them... or it might have been enough to break him, because his later novels were a bit more cynical on the matter. Hard to tell, without a time machine or a really good necromancer.
You can also see Heinlein was pretty cocksure about his opinions and I suspect as an RPG.net poster he wouldn't have lasted very long, but that's neither here nor there.