The current slang term for orbital kinetic bombardment among sci-fi authors, fans and even scientists and engineers whose job it is to work on such things? “Dropping rocks.”
Entirely separate from the idiot’s other issues, they are absolutely correct on this matter. Not on much of anything else, but this one point they are right on.
Agreed that the physics makes it possible...that is hardly the same thing as a sure thing. Having no way to correct for recently angles one could as easily be skipping off the edge of the atmosphere as inserting into it.