Report the light to the city. If you've reported it and you can demonstrate that it's broken (won't change for your legal vehicle) then in most states you're allowed to treat broken lights as though they were blinking reds (go when traffic clears).
IANAL but I would think having reported the light as broken gives you a more firm ground.

Just out of curiosity, did the cop acknowledge that it was possible that the light was defective? Did you ask him what you SHOULD do for a light that won't change? What should a car do?