It really depends on how deep that is. You can buff it out with a mild compound and see what happens. Then hit it with a polish. Just remember, mild compound. You go to heavy a grit and you'll leave marks. You're just looking to hand polish that out. Ideally its just damage to the clearcoat. If so you can make it look nearly invisible with the right buffout. If they got into the paint, then you'll need to touch up or have the doors repainted.
That's a **** shame BTW, why the fuk people do that, I just don't get it.