A nuclear missile is a projectile moving at high speeds, and from what he is saying, from the Earth, up to orbit, to the station.

I am saying that the station would detect it and use the satellites' manuevering rockets to move into a lower orbit, and use lasers and railguns to intercept the missile. I'm not saying that they are 100% accurate, but I AM saying that if you fire a missile like that from long range, or extreme range, then I [u]will[/u] detect it, and I [u]will[/u] move defenses in its way. Interceptor missiles, pulse lasers, light railguns. 

If you want to hit the station with a nuclear weapon, bring up a ship to deposit it within a range too close for the point defense to wipe it out. I've been reading all about interstellar warfare, and quite simply, you gotta get close. If you fire a great deal of them, 5 or more, then I would not be able to efficiently counter them, if they are fired at the same time. Two or three would get through. 

I am not saying I am invincible. I am saying that you can't just fire from a long distance and forget about it. It won't work. The Ceres Independence is the only nation that is exclusively space-based, with some of the best space-centered technology. They have sublight, though they won't say anything about it. If they could get it into a small enough shell [which won't happen for at least fifty years to another century], then they could make a sublight missile that really would be impossible to intercept. But if you fire a regular missile from Earth to target the New Point station, then it will be intercepted. One missile would mean the end for the Ceres Independence, because they currently can't build another station, nor could they be able to reestablish trade with their clients on the ground, and one of two storage spaces would be gone. It'd be disastrous, and there would be no saving the Ceres Independence. Shuttles could still make it, but it'd take a toll on them to keep going back and forth, and the mining ships are too slow.

Quite simply, it's perfectly plausible to keep a nuclear missile from hitting New Point, and New Point is one of two population centers of the Ceres Independence. It'd be like taking a missile and wiping out a fourth of the US in one hit. I couldn't, can't, let that happen, or it'd be the end.

So if a single missile can take out New Point, regardless of its defenses, then there isn't very much point, is there? The Ceres Independence is so advanced, but they are also very small and vulnerable, whatwith being remote. They can't afford to [u][b]not[/u][/b] take precautions to intercept nuclear missiles, or some other kind of weapon that would destroy the New Point. Strategically, the New Point isn't worth much anyways without the Ceres Shuttles. They are the only ones with the right docking rings, and the station doesn't have an orbital weapons. All the satellites can do is move very slowly, for a very limited amount of time before having to get more fuel. All the station can do is act as a communications hub and storage bay. And as a town, since the Ceres is short on space. 

What is it, tl;dr?

Tl;dr, it's too dangerous to allow one of two Ceres population centers to be easily taken out with one or two missiles, so the station has its own defenses to protect against it.