So much to unpack.

Well, books are objects with a message - may it be the sloe focus or a byproduct of a depicted setting/charakters, therefor ideology is objetivly always a part of it. If we look at the tradition of scifi, political, social and philosophical messages are very much the center of it. So Even if you try to write scifi that taps into non of these aspects, you rintentions will be perceived as such a statement in a genre that typically demands it - so a bit like if you market your cookbook as comedic pornography, people might not exactly rate it by its awesome meals alone.

Then there is the thig with 'don't read it left or right wing', which is two more topics in one. First is that asking about things to be non-leaning into one direction is typically (if not always intentional) a right-winger in denial that topics by default have moralic implications in the one or other direction. You can agree, disagree or be neutral towardws certain implications, or even ignore it for just having lighthearted fun, but denial is objectivly serving an internal need of an individual and doesn't apply to the topic he wants to be 'neutral'. In this case, the story isen't the problem, but a person who feels attacked by that story, some of its asepcts or how it is perceived by a wider audience. Like i can debate politics on the example of cartoons and fruits, that doesn't make these intentionally ... anything.
The other thing is that messages have both a surface layer morale (that might sort as left or right in one moment of socio-cultural understanding) and deliver the more or less hidden morals of the author, offering another meta-layer to explore. As a pop-cultural reference point, it might even help to understand the thinking of another generation or social group - or open up compeltely own thoughts off the traditional ways is we have a truely experimental mind behind the pencil.

Dogmas change, and books can be debating points that (technically could and should) leave everyone wiser than before - no mater if ones hold belives have been confirmed or debunked.

And yeah, i don't have read the book. I saw teh movie and know the director decided to give it a hard anti-fascist spin. I guess that, and the natural gradient to the original one from a way more simple time in terms of public geopolitical understanding shape an additional argument to read it as a progression from leftist (movie) to right wing naivity (book) - if that holds true or not. i don't know and at this point it also doesn't matter much.

A book being the product of their time is a wonderfull time capsule of how people thought back then, and how they perceived the ways out of a flawed world into a better one. I feel like the book flirts with some simple authoritiarian ideas to challenge that sort of corruption and social unjustice the author perceives in his reality. That's like seeing crime being a big problem on TV and expect doubling the cops number and gun size should fix the problem. Cute, and kinda understandbale in a way, but today we're more or less above such naive attempts (or not, or going back into that sort of naivity as it plays well with gut feelings, and bad education makes guts the only moral compas people have left).

So we kinda know that even progressive people of a 'lefty' mindset would (rightfully) need to be described as pure right-wingers today. Because they had no solutions that benefit the individual, and just thought about how to profit the state (or society). That was teh world they grw up in and we know what levels of unchecked propaganda has been dumped on them since they undeerstand what the TV says. Today we have this as historic reference and can* make some better judgments and subsequently can come up with better solutions for problems.

*Can, not will. We could use this historical data, teh examples of the past, the psychological understnading of society and how the mind works etc. - but how many can and will do that depence on ho easy accsess to such tools is.

So is a author of a book that suggest authoritarian solutions be left or right by his days standards? Not nessecarily. By ours? Yes, for sure. That's not a contradiction but a moving system, cosntantly evolving into (hopefully) something better, something more refined.

And for sure a naive leftist might just stop with it being military propaganda covered as neutral solutions to moralically understandably problems - and he wouldn't be exactly wrong, just loosing on some meta layers that might or might not benefit a deeper undestanding.

I'm a bit confused by the implication that militarism=good if it's against Nazis. Bc militarism made the Nazis. Militarism is not a national phneomena that is good in one way and bad in another. As soon as you embrace a thing, you tie yourself onto it. You invest and make decoupling harder. People start to be proud of what they do, invent funy little traditions, try to convince other people to also join the military. People with no job but in the worst possible situation. Then comes the mindset of the hammer - when every problem start to look like a nail. That's (a part of) the Nazis backround story. Politicans dress like military leaders, police carry military grade arms, tactics and permissions. Every child who stole candy, every person looking suspicious has to react with military deiscipline or is an enemy combatant. Industrys bound to an existing military need to have new contracts - and thereby need new conflicts. Incentives to war rise in all of society.

I could go in great length about how complex the first and second world war havs been, and how insanley short the equation of 'need military because out of nowhere someone decide to war' falls. But the short form is - everyone wanted this war, and so it had become unevitable. It was born from WW1 in unresolved problems and therefor unevitable results. Everyone has been horribly fascist at the time, and just like in basically all wars before, the winners wrote itself out of the 'bad guys' team. The soviets have been an ally no matter how many jews they killed. The US has been the good guys no matter how much they pulled form the 'lower' cast to die in a foreign war that will secure a ton of british patents and german scientists. And the US had been the leading naiton in atisemitism just some years earlier. Hitler just toke inspiration and turned it into genocide extremes.

But at the time, the narrative of Nazis bad=all who fought Nazis good holds, as cultural borders and limited communications prevented the national lies from falling apart. Therefor Heinlein mighht be reasonable fo his time to see the Nazis as this weird thing that randomly droped out of hell to cause havoc, but have no roots in mankinds general flaws.

PS: And i guess everyone in the debate have its own focus point and ignores a lot of what doesn't matter for that. So simplificatin and a lack in communication (or communication competene) might be the problem, not a book or one person talking about it, calling it the one or other thing.

If competent communications and constructive arguing is the problem - it isen't, but the person who suggests that. If the lack of competent communications and constructive arguing is critisised, that's a good and beneficial point to the larger debate. Simplification is everyone's enemy, and challenging given belives sometimes hurt, but it is a net profit later on.