While I agree that AppleTV should have more granular parental controls regarding Netflix that just "Ask, Allow, and Hide," there is another way.
It's called "Account Profiles."
Here's how to set them up:
1. On your computer, go to the Netflix web site, sign into your account, and go to "Your account and help."
2. Look down the left side of the page for "Preferences." You will see an option for "Account Profiles." Select that.
3. Click "Add profile"
4. Configure your new profile with whatever name you like, and a different "sign-in" name than your normal account. This is where you can set the profile to only allow certain content ratings. Set them up as you see fit. Click "Save."
5. Go back to your AppleTV. Logout of the current Netflix account, and log back in using the Account Profile sign-in ID you created on the Netflix web site. Yes, I know AppleTV says to put in your email address, but just put in the Account Profile sign-in instead.
Now your AppleTV can access Netflix, but the content on Netflix will be limited by your settings in your Netlix account profile.
You can go into Parental Controls on AppleTV, and simply set "Allow" for Netflix, since it is managed separately.
This worked for me, hopefully it will help others.