Well, in The Moon is a Harsh Mistress, they had a bit of a revolution on the moon and started throwing rocks. Having the power generators situated on earth would keep that scenario at bay.
Still I wonder how dangerous a mass driver launched rock from the Moon is as long as the mass driver is originally configured for cargo launch, so "just" a few km/s.
Still could do quite a bit of damage if it hits something but if it does not do any.manuevers &could be detected, then there should be ~days for arranging something to collide with it and turn it to plasma or dust.
But I guess if they could spam it & be creative with the resulting trajectories. Still the mass driver is fixed on the Moon surface, so it might not survive for long until it is itself hit by something in retaliation.