“The short version is that the moon is the ultimate high ground and there’s no way to intercept such projectiles in a meaningful fashion.”
Yup. First thing I thought of too (having read my Heinlein!). OTOH, I don’t see how we can really object to them putting a station up there if they want to. I mean, on what grounds? “We think you have an aggressive viewpoint and will someday want to lob rocks at us?” True enough, but really, impossible to prove.
The best way to control what goes on up there is to be there ourselves, either on Luna or nearby.
Not to mention, we can object all we want and there’s not a damn thing we can/will do about it. Obama has reduced us to “also ran” in terms of space expansion.
Another turd in his “legacy”.