NSSO on Space Based Solar Power
Changing the focal length, or the effective focal length is rather simple.
For example, build a space based heliostat. Then your just need to keep the reflectors flat. When the mirrors are large shiets of aluminum coated mylar, the problem will be simpler than the earth based equivalents
The nice refutation forgets a few things, like there are currently no publicly known weapon systems capable of disabling a device above LEO. Any nation that could get to GEO could maybe weaponize a payload, but if I owned such a death ray why would I let anyone launch a rocket that I hadn't inspected? Or conversely, the trip to GEO takes a while, a long while that the weapon would have to retaliate. Launch 3 or 4 of them and keep the entire planet under guard at any given time.
Bombs cost money, sunlight is free. After launch the devices would be about untouchable and would never run out of ammo. The same can't be said for the US Military.