Spaceflight is the ultimate achievement of industrial civilization. That is debatable, but in terms of utilizing all parts of industry simultaneously, no other single activity even comes close. I don't think it is a coincidence that it became popular to say the Apollo moon landings were faked around the same time that US manufacturing was seen to be declining. In case you're wondering they're both urban myths.
Mere understanding of how industrial civilization functions is lacking in the popular consciousness. Quick, where was your chair made? That one is probably too easy. What's it made out of? Where do each of those materials come from? Which processes are used to refine them? How are they transported? How are they combined? How much labor goes into each step? How much electricity is used? How is the electricity generated? Almost certainly all your answers are wrong and just finding out would take years.
More dangerous is the assumption: none of it is really necessary. Industry is seen by some as the means by which consumers get plasma TVs and video game consoles. They say the really important things in life - food, shelter, medicine and love - are not made in a factory, or at least need not. They advocate a return to a pre-industrial age where subsistence farming isn't a haphazard drudgery and natural remedies are just as effective as modern pharmaceuticals. Where "living in harmony with nature" means something more than squatting in the dirt.
Discontent with modern life is the inevitable result of a general ignorance of how outright fantastic it has become. It's not just the failure to study history - although few understand how advanced the Romans were compared to the dark ages that followed their conquest by hordes with no apparent appreciation for advanced culture - it's the failure to write history. I've read many books about Apollo, but I've yet to find one that explains where they got the metal to build the command module. We don't write that stuff down, it's just considered part of the background noise. Similarly, the only people who talk about where steak comes from is militant vegans who want to put a stop to it - and typically a good chunk of the rest of modern life.
Who cares what a bunch of hippies say? They have the right to their own opinion, right? So long as they're not hurting anyone... ahh, so there's the line. Do we have to wait until actual violence before we tell them they're wrong? If they're advocating violence can we move beyond verbal education? What happens if they win?
I think we have to consider that last question. Last time the hordes won, the dark age lasted ten centuries. Humanity took a few hundred years more just to get back to the level of Nepos and we have no idea how much was lost in the fire at Alexandria. So long as "returning to nature" is seen as a viable alternative to industrialized civilization, the threat will exist. I don't think there's much value in making the argument that we passed the no return sign long ago, as most rational people already know.
To me, it comes down to this.