Whew! Thank you for the many and entertaining responses!
I'm going to attempt to summarize what I read so far and throw in a few more own thoughts and follow-up questions. Don't hesitate to correct me if I got some of your ideas wrong. The main points in this thread so far seem to be (paraphrased in quotes, with my comments below):
1. "I suffer from lack of freedom in a dead-end boring job, so I want FIRE." This doesn't sound logical to me. Why wait until (early) retirement? Why not simply take on another, better, more interesting job? Wouldn't that be more badass than accumulating your stash while feeling like a victim?
2. "I wanna do what I love / find enjoyable, therefore FIRE." Yes, I get it, but this is besides the point of the original question, which was regarding the badass attitude.
Currently, I find it enjoyable to read books and watch YouTube videos in my "non-work" time.
I must admit I don't really have a deep drive toward any great achievements outside of my profession (I wish I had) nor do I have any other qualifications to speak of (not so sure if I should seek them, though). I do, however, realize that if you don't put pressure on people like myself, they will underperform by default. If you are isolated from competition, it's very easy to trick oneself into thinking that you're "doing just great" while in reality you're just mediocre. For example, top scientists are working for universities and subjecting themselves to peer review all the time, not writing up their theories in online blogs and founding circles of admiration (this is what the kooky "alternative" types like to do).
3. Losing the hardly earned skills and status. Yes, this quite concerns me. Once you drop out of a profession (or even, in some lines of work, "retire" from industry into academia), you fairly quickly lose the edge and maybe even touch with reality. Let's not fool ourselves, from professional perspective it is the continuous training that makes us the real badasses, and it is conceivably less likely that you will train yourself just as hard when you declare yourself "retired". Others won't expect it from you either - "oh yes, he was a great <insert profession here>, pity he's now retired (= can't be relied upon)". So there is certainly a loss of social status. Which some of you say should not concern a real badass all that much. But I beg to differ - a badass for me is someone who others look up to, not some sort of "anti-social hermit prick indulging in his hobbies" together with a bunch of friends/groupies. (It's telling that this is often the behavior of people who came into their riches by means of inheritance or being born in a rich family; they are generally a rather sad bunch.)
4. "I just wanna do X (or don't wanna do Y) - I owe the world nothing!" and "I wanna grow as a human not as some robot worker!" To me this sounds very much like something our spoiled hermit prick would bring up (and I will admit, being a lone wolf myself, it does sound alluring). It also fits the concept of "FU" money, "independence" and "self-sustainability" nicely. Unfortunately, these are rather childish concepts in a highly interconnected modern world.
Thinking it over, I agree that you don't owe the world to stick to a shitty dead-end salesman job, slaving away for benefit of your ideological enemy, or some such. But I sense there may be inherent joy and gratification in actually acting as if you owed the world something (rather than in the opposite way).
This seems, at first glance, compatible with the idea of retiring to do more community/charity work, but I am also suspicious of that argument, in a Randian sort of way.
In a capitalistic society money/income has a signal function - the "more important" types of work, as perceived by society, tend to pay more than the "less important" types simply because they are harder to substitute. Consequently, consuming and having fun tends to pay nothing - these activities require you to compensate someone for your abstinence from producing. So as I see it, it would be honest enough to claim "I want to give up producing as soon as I can, so that I can consume more". But it's not genuine to call yourself badass at the same time - you're then like a disciplined alcoholic who is waiting to afford themselves a lot of drinks later (while possibly showing off toward some of the less disciplined friends who can't abstain from the regular habit). Not exactly a role model!
5."But Raay, the whole badassity is just a means to an end and has always been meant so!" (the end presumably being future relaxed consumption). Okay, if you put it so, I am satisfied, but then the answer to my question "does early retirement contradict badassity" is a definitive YES. Then we should each decide which will make us more happy: early retirement or actual badassity, but please don't confuse them with each other.
6. "Stoicism is not masochism - not about needless suffering or deprivation!" I agree, and I think MMM does, too! In fact stoicism in its modern wrapping of badassity is about hardening yourself to achieve more, become less prone to suffering, and get more satisfaction from what you achieve (not in the least by comparison with other less badass folks who tend to fret about nothing or suffer from their perceptions of unfulfilled entitlement).
In a sense it (as it often does) comes down to the definition of what "retirement" means. To me, and I suppose to most people who hear the word, it is something along "doing what you want, worry-free from economic and maybe also other external constraints". I guess my own doubts boil down to the point: does retirement (early or not) really bring satisfaction to the retiree? And if it does, isn't this a sign that the retiree has screwed up before retirement and then "managed to get away"? Certainly, managing an (early) escape is better than not, but should this even be our goal? Isn't it just plain lazy and self-degrading, given how easy it is for saving-savvy high-earners in developed countries?