It's a very tricky issue, TwoWheels.
One the one hand, you're right. People absolutely do have the freedom to make different choices, including not following the mainstream.
But that freedom that you and I experience isn't necessarily as true for everybody in America. It presupposes a good enough education to have both literacy and numeracy, or at least the ability to learn both, and the latter in particular is far from universal. Pretty hard to make investments if you can't read well or don't have basic math skills.
You have to have regular access to the internet and enough free time away from work and children to spend hunting around on it in order to stumble across a site that points out the possibility of FIRE (I'm frugal, but I wouldn't have come up with the MMM/ERE "system" on my own. Would you have?). How often does it come up in the forums how unsupportive people's friends and family are? Even if you did figure it out entirely on your own, without the resources of the forums and other people who have proven that they can do it, I think many people would start to question their plans when everybody around them universally thinks they are crazy for trying.
Humans are social creatures - much of our learning and understanding of the possibilities that the world offers comes from the people around us. We do absolutely have the freedom to ignore all of that, but it's not as simple as snapping one's fingers and saying "ah-ha!". You have to have intelligence, education, discipline, and a bit of luck (like, say, not getting pregnant at 14) to pull it off. I love that MMM and ERE treat people like they're smart enough to figure it out for themselves, it's an incredibly refreshing attitude, but unfortunately it isn't necessarily the case if you don't have the basics of logic and reasoning down.
So that's why it makes me angry.