But, to be honest, I don't know what else they could have said or done. They probably shouldn't be fully transparent and say "we tried a way to shear the sheep and the sheep did overreact, let's try another way".
This could be followed with a brief account of how they actually see advertising working on the site (hopefully it's not stupid or creepy), making a retraction of the bad terms, and saying that they'll be revising the terms to support this direction and this direction only.
Finally, they may want to acknowledge that users have every right to value their IP highly, and that Instagram knows that while their service is popular, it doesn't justify the kind of liberties that the bad TOS was taking with IP that isn't Instagram's in the first place, and what they're really focused on is a trade that everyone sees as fair. They can add that they appreciate people's patience as they take the time to get the exchange right.