Is it really necessary to spell out that a civilization capable of building a FTL starship is also capable of building a sufficient defensive technology?
> I daresay such a civ is not doing it for conquest, but to discover and explore. If the urge is militaristic, then such a civ would turn on itself long before the project succeeds.
I think this is much more complex. Consider a civilization so advanced that this is children's toys for them - and then that civilization falls. Then, on the scraps of it, a new military dictatorship is built and they go for the conquest; they don't even need to understand the magic that powers their warships. I recommend you to read the full Foundation series in chronological order.
We have had ICBMs for a long time, yet no sufficient defensive technology as of yet.
Beyond the fact that using them would lead to MAD, that is.
Or it will pass through a planet like neutrino. How you know which FTL method will actually work?
Sure, FTL travel is never grounded in our understanding of physics and the universe, but do you really think our understanding is anywhere near complete?
My favourites are from Futurama:
1. Scientists increased the speed of light in the year 2208.
2. "The [Dark Matter Engines] don't move the ship at all. The ship stays where it is and the engines move the universe around it."
Neither Star Wars or Star Trek do things well. Some other material does things reasonably well explained and thus actually are on Fiction side.
Hardest possible take does not really leave too much room to go around. Some expectations make more interesting stories and explorations.
But yeah, thank god most of science fiction is actually fantasy because if any of those things were possible, they'd immediately be used to destroy planets. Ships going FTL could be collided into a planet. Teleportation and easily accessed anti-matter could be used to annihilate cities - or planets. Most authors don't even bother building in reasons why that can't happen, its just that no-one thinks of doing it.
I think the limits of the real world are quite fascinating. It's almost like reality was designed to support a huge array of civilizations that cannot interfere with each other. Interstellar travel is so hard that any civ capable of it is going to be capable of executing technologically advanced projects over centuries or millenia, and I daresay such a civ is not doing it for conquest, but to discover and explore. If the urge is militaristic, then such a civ would turn on itself long before the project succeeds. There's a kind of poetry to it.