1) That you can actually get rid of gender bias among corporate boards that are almost entirely men;
2) That the system isn't path dependent (i.e. removing the positive discrimination will result in an outcome that is the same as would have been the outcome if the positive discrimination had never occurred).
Real-world systems are generally path-dependent. If a storm knocks down a fence, the fence doesn't go back to normal after the storm passes. If you bend a paperclip, it will stay bent after you let go.
Taking affirmative action off the table is tantamount to saying that society simply should not fix problems that result from the path-dependent effects of prior discrimination. Now that's debatable, but I don't think either side of that debate is "lazy."
FWIW, I think the California law is probably unconstitutional. (The Constitution doesn't always say what you want it to say!)