This is good to know. I'll at least read "The Moon is a Harsh Mistress" soon, and likely will read some others over time.
I'm not a huge sci-fi reader, just the classics really, but it's a little unfair to say that there isn't anything "even vaguely libertarian" about Bradbury. They guy wrote "Fahrenheit 451". Even short stories like "Sound of Thunder" involve strong libertarian ideas. To my knowledge he didn't espouse libertarian theory, but he certainly pushed for a more educated populous and against totalitarian rule. The other ones were all world government types, but their science is sound.
As for characters, well, to me that isn't what sci-fi is about. To me, hard sci-fi is about ideas backed by what would at least be considered possible given our knowledge at the time. It looks into the future and considers the ramifications of different technologies. I can't name any characters from Asimov, and can only even recall the two debuggers from "I, Robot". However, a few weeks back a Swiss data warehouse consultant, an American machine learning doctorate, a brilliant Indian semantics/ontology guy, a high level Indian programmer/IT manager and myself were able to talk about the laws of robotics, their value and how they would work going forward for two hours over dinner at a Punjabi place in Delhi. Who else could have sparked that kind of conversation 50 some years after their relevant books were published?
It's hard to take most political stuff in sci-fi seriously. Even Card in the 80's assumed that the Soviet Union would live forever. They all more or less lean toward technocratic rule. Where they shine is in their vision of science/engineering and showing the failings of technocratic systems.
"Freedom suppressed and again regained bites with keener fangs than freedom never endangered." -- Cicero