The route that they are going, is NOT defensive. It is OFFENSIVE. Look, lets say that the west decides to launch against China. By the time that China realizes this, the ICBMs are on their way and have already switched off from sats and are working with intertia systems.
Where anti-sat systems come into play, from a military pov, is knocking out the enemies eyes and communications PRIOR to your launching first strike.
China is busy developing a first strike set-up, that is useless for defense.
In addition, it is now known by the general public that China has active nuclear work going on. They can claim only 300 warheads, but, why hide a nuke facility underground and by a lake then? There was no reason for it, UNLESS you are up to things that get around treaties.