I doubt it was seriously considered at the time it was discussed. Space Stations are in orbit - the space battleship doesn't have to be, that is very significant.
Earth is spinning in a giant circle around the sun. Thats facts. "aiming an asteroid" is less of making a rock a missile - and a lot more of tug-boating it into the exact right spot, in the way of earth, so that earth hits the asteroid - not anything complicated like the asteroid hitting earth.
There are a lot of little things like that...
> Space Stations are in orbit - the space battleship doesn't have to be
I mean, you did say:
> space battleship - one that never comes down to the surface, just sits in orbit.
So I think it's understandable for people to take that at face value.
Furthermore, if it isn't in orbit, then where would it be?
> and a lot more of tug-boating it into the exact right spot, in the way of earth, so that earth hits the asteroid - not anything complicated like the asteroid hitting earth.
From an orbital mechanics standpoint I don't think there's actually a difference. You're changing an orbit either way.
Any realistic space warship design will need propellant - sure you can avoid ground based interceptors and kill sats but it will eat into your propellant reserves over time.
You will need to replenish from somewhere & that somewhere might as well get nuked instead of the ship, rendering it useless.