> People need to understand that if you’re being attacked by a FTL capable alien invader, you are so incredibly f*ed that it just does not matter.This, and I'd raise the bar even further: if we were to be attacked by any alien civilization, no matter if they have FTL or other Clarke tech or even if they have no special tech at all, we're incredibly f**ed.
It would be trivial to hurl asteroids at us until we're all dead. It would be trivial to engineer deadly pathogens, or to flood our planet with hunter-killer drones, or to roast the Earth with solar mirrors. And those are just the low tech options. We chose not to colonize the solar system, and thus we have no possible way of countering a civilization even if it was on the same developmental level as us.
Maybe we'd be able to mount a counter strike against one alien craft if they're unlucky and don't eradicate us outright. But that's a very big if.
However, I sleep well at night knowing that we have so far not seen anyone else out there, and we definitely have not seen a large space ship entering our system. Assuming they're bound to known physics, we'd definitely pick up their deceleration burn as they approach. If someone wants to eradicate us, a risk-free strategy would probably be to bombard us from outside the solar system.