Unown G does not prevent the extra damage. It is just that, damage. Bash In only checks to see if there is a Tool attached to the Pokemon, it does not place an effect on the Pokemon in any way.
See that + next to the 70? Since the defending pokemon has Unown, imagion the 70 to say 70+60. That's how I remember. If there's a + or a X next to the damage, it isn't an effect. It's damage.