An invasion, or at the very least a replacement of the people and culture of a country being done legally does not mean it is not a problem. And giving more political power to the people who are coming in and outbreeding you will accelerate the timeline of the issue and weaken the power of the ones who can stop it. Policies related to birth rate need to be thought out very carefully as you can incentivize the wrong thing.

Having since read more about the author I'm pretty sure you're right the novel was earnest, but honestly it read as excellent satire when I didn't know it wasn't meant to be (and I read it prior to seeing the movie). Would recommend.

Then you're against democracy. Think about what the word means.

It's worth noting that in the book "service" is heavily implied to be primarily military in nature yet Heinlein purported years after the fact that in the book's canon "95 percent" of citizen service was actually civil. I think it's debatable whether or not this was his intention all along or a retcon to fit his more, ahem, liberal worldview that emerged as he aged.

I also loved Verhoeven's film adaptation but he straight up admitted that he didn't finish the book before making the film, which was itself based on a Neumeier (of "Robocop" fame) script called "Bug Hunt at Outpost 7" that bore only superficial resemblance to the book. He made the same mistake as many others in casting the book as fascist merely because of its militaristic elements when it's clearly not. On top of lacking many essential elements of fascism (a dictator, a directed economy, suppression of political dissent, etc) there are also several spots that veer into philosophical treatise to espouse the opposite. The flashback scene involving Rico's professor talking about how a society is obligated to raise its children correctly (and how it's society's failure if they end up delinquent) is a perfect example - "the system is the problem" hardly reads as far-right.

This is all to say that I think Heinlein was more interested in exploring a concept of reciprocal responsibility between a citizenry and its government. The militaristic aspects of the novel as regards a distant, dehumanized enemy and the dominance of the fight over all other aspects of life are far more alarming in my opinion.

Or policy. We have an embarrassing chap in these comments advocating for the equivalent of Jim Crow voting laws.

Did the government not provide you with services (roads, police, etc) in those 40+ years?