Further: if you dig into Gini by cities, your hypothesis gets even weaker: one ranking I found goes:
1. San Juan
2. Atlanta
3. Miami
4. New Orleans
5. New York
6. Cleveland
7. Cincinatti
8. Dallas
9. Tampa
10. Chicago
(I'm playing with the actual ACS data from Census.gov now, but haven't figured out how to get it broken out by major city; if you do by "places", which include every city no matter how small, the leaderboard is dominated by small rural cities).
No California city even appears in the top 10, and the list is dominated by non-finance-centers in red states.