Every characteristic needs to be secret just in case someone decides to murder everyone with that characteristic.

If that is going to happen in the US it is probably going to be a red/blue culture war thing. Shall we eliminate campaign finance transparency?

Knowing where your Jewish friend lives is fine. Having a list of every Jewish person in your zipcode (or every X) is like holding a handgrenade.

When the Ashley Madison hack happened a whole mess of blackmail was the result.

I have had someone target me in an attempt of blackmail due to a forum breach (why they thought an anime forum was good blackmail beats me...)

Your browsing habits, which is a step removed from PII, even reveals your sexuality and pregnancy status.

And, we had an attack on Jewish people in the last month. We have not had anyone Democrat/Republican hunting.