[mopsi]

> As a counterexample: the military has had supersonic jets for two generations, and there is no civilian supersonic transport. The only one that did exist was an european undertaking.

This undermines your main argument, because it shows how the military explores territory that would otherwise remain largely unexplored.

[sneak]

...with no benefit to humanity, only huge financial and humanitarian costs. That’s the argument, and it is a perfect example.

[mopsi]

The benefits of military research are often non-obvious. Supersonic flight needed fine control, so electric flight control systems (fly-by-wire) were developed and put into use on fighter jets.

When Concorde was on drawing boards, the same tech was re-used and developed further. Supersonic flight turned out to be a dead end, but the control system developed for Concorde (originating from fighter jets) proved valuable and was carried over to later Airbus A300 and Airbus A320 designs, and has given remarkable safety improvements.

While we don't have supersonic flight in 2020, the legacy of early Anglo-French fighter jets and commercially unsuccessful Concorde lives on in every Airbus plane and many other influenced designs.

[sneak]

What evidence do we have that any of that military technology was directly reused in the civilian applications? Furthermore, to make such claims is to say that the military developing this technology, plus the associated mass murder that results, is somehow a better deal than privately paying to develop this technology from scratch independently without the associated violence.

It’s the second part that is the nut that your argument must crack, and that is a very difficult bar to clear indeed if you in any way value human life.