On Starship Troopers:
Okay, this is the way it worked. First of all, it was clear in the book that you just had to do a stint in ‘civil service’. In Juan’s case, the only reason he wasn’t offered civil service jobs was because HE decided to fulfill his obligation by joining the military. I imagine if he wanted to be a government meat inspector he would have volunteered in a totally different place.
Once you decided to join the military, here’s how it worked: You could list your preferences, and they would do their damndest to put you in one of your choices. But there are no charity cases allowed, so you still had to meet all the physical, mental, and psychological requirements for your requested service.
If you didn’t qualify for any of the things you wanted, then they would decide where to put you. HOWEVER, in that military you have the option to quit at any time, other than during combat. ANY time. You could quit before shipping out, quit in basic training, whatever. Lots of people in the book did just that - in fact, Johnny Rico himself came within a whisker of quitting. And remember, during the recruitment process they did everything in their power to STOP you from joining, up to and including horriblly disfigured casualties at the front desk to scare you away.
Also, no one could be refused service. This was important to prevent the military from becoming a closed society antithetical to the civilian population. ANYONE could serve. The catch was that if you weren’t qualified for anything but insisted on serving, then they’d find something you could be even marginally useful for you to do. And if that included being an ice inspector on Pluto, then tough noogies for you. Of course, you could always quit, but if you insisted on serviing, you went where they told you.
And if you did quit the service, you never, ever got a chance to sign up again. Service is supposed to entail some sacrifice, so it was not supposed to be a country club where you could come and go at will. Leave before your time is up, and you’ve proven yourself to be a little to selfish to be trusted with the vote. Sorry.
The idea here is that they wanted to make sure that every single person in the military was there because it’s exactly where he wanted to be at that time. Heinlein himself was virulently opposed to conscripton - he thought the draft was a form of slavery (which it was).
The whole purpose of this structure in his society was to make sure that the people who voted were the kind of people who were likely to take their responsibility seriously. As he saw it, one of the main flaws of unlimited democracy was that once the people realize they can vote their own bread and circuses you’re in big trouble. Starship Troopers was a thought experiment on how you could set up a limited democracy while retaining a ‘do what’s right for society’ focus among the voters.
It had absolutely nothing whatsoever to do with Fascism, which Heinlein believed was a truly evil philosophy.