Interesting, but I disagree with a lot of Eric S. Raymond's history and conclusions.
The main problem in his politics in SF essay is you have to consider the source and possible bias. Eric is a Libertarian who likes hard science fiction. Is it a surprise he writes a history of SF where his preference is the "true" science fiction and that he considers that it is also libertarian science fiction? Are you surprised that he expands on this to state that the other movements in science fiction are unsuccessful communist, or liberal and communist, reactions to it? There is some truths in his history but his overall bias is very evident and is not the normal
An essay of his just discussing science fiction without politics is much better, very useful in understanding SF, - SF Words and Prototype Worlds.