Lets face it, the founding fathers didn’t foresee our technology and people being able to own automatic weapons that could singlehandedly defeat entire musket armies.
Who is to say the same thing won’t happen to us? Nobody disagrees with people being able to own cars, it’s essentially a requirement. But what about the next few hundred years when a commute could be to orbit, or another part of the solar system, or even another star?
The energy involved in these kind of technologies would be immense. Something with the power to transport a ship across the solar system, or go FTL using some kind of exotic physics would be able to output some serious energy. Probably the simplest and most provable is antimatter engines. They are entirely possible today, the only problem is antimatter is currently way too expensive to be used as a fuel. However, if you filled up a bottle of antimatter in your spaceship, if you misused that, you would have a weapon that would make a 50-megaton bomb look like a firecracker. You could singlehandedly wipe out an entire city with millions of people in it.
Nobody could even really predict how destructive those kinds of technologies could end up when misused.
In the future, should technology like that be able to be owned by civilians, where anyone could kill millions of people as easily as crashing a ship into a city?