The best response to a narc is no response! If you must respond, show no emotion... This can be very difficult, but it will deprive him of what he wants most... A narcissistic payoff from your reaction/response.
Saying no to unideal clients/people/business >> Sometimes walking away has nothing to do with weakness and everything to do with strength. We walk away not because we want other to realize our worth and value, but because we finally realize our own.
If you’re feeling pain, don’t take action that creates even more pain. Don’t try to cover darkness with darkness. Find the light. Act out of love. Do something that will enable you to move forward toward a more fulfilling reality. There is always something good you can do. There is always love to give. Fill your heart with it and act in everyone’s best interest, especially your own.