Not to defend the blue, bald statue in the Tower, but I believe the Drifter indirectly helped in aiding the enemy on the moon by tempting some of the special task force Guardians that Zavala placed on the moon (which, yes he did quarantine, likely more for Bungie not having made a Moon area in D2 yet), that dwindled that force. Also, Eris Morn was there as well, and if I'm reading the lore correctly, she had a hand in stirring the crap that's starting on the Moon. Not intentionally, though. Lastly, no Hunter Vanguard has been selected yet.
LOL. I called him a statue too. We're on the same wavelength. To me, he's just a speed bump for any enemy racing in to take the city.
Not even speed bump to enemies like Gaul, who just cruise right over the wall, guns and missiles firing.