I think we would all be better off if we didn't develop even more effective ways of killing each other...
b) There is a reason we don't use Trident D-5 SLBMs (or the Russian equivalent) for precision conventional explosive strikes on targets which otherwise require long range bombers with intricate in-flight refuelling arrangements to hit: something about not scaring the other folks with strategic nukes into thinking we've initiated a first strike and hitting the big red end of the world button.
TLDR: even the big guys don't mess with space-based or sub-orbital weaponry. The risk of a misunderstanding is non-trivial and the perceived costs are far too high.
It's probably most cost efficient to de-orbit the entire satellite, and include a rocket that fires upwards when it reaches a certain low height, to make it exceed its natural terminal velocity.
I expect an arms race in this area.
There are also plenty of rocks on the Moon, but I don't have a good feel for how practical weaponizing them would be.