Exactly. Thank you.

The slippy slope here is already in operation. It's the entire rationale behind prohibiting targeting based on zip code: demographics change from zip code to zip code, so the HUD concludes that targeting by zip code is de facto targeting by demographic.

What logical basis is there for stopping at zip code targeting and not applying the same logic to other demographic correlates?

I'm not sure people understand the inevitable progression here.

Step 1: HUD files a complaint against Facebook for allowing ad targeting based on certain criteria.

Step 2: Facebook bans advertising targeting based on the criteria in the HUD complaint.

Step 3: Advertisers react by targeting based on demographic correlates of the categories from step #1.

Step 4: HUD notices that ads are still getting delivered more to one group than another.

GOTO STEP #1.

There's no clear point at which this process stops. Demographic correlates are numerous and strong. Are you going to ban all of them? That's tantamount to banning ad targeting generally!