I also submit that if you think discriminating against blacks and women was good for business (a defensible claim), then you probably ought to be disagreeing with Tim Cook about whether sexual-orientation-based discrimination is good for businesses [1]. In my view, that would make the case for anti-discrimination legislation stronger, not weaker, because if both prevailing biases and good business sense favors discrimination, then we really need to act.[2]
[1] Perhaps you could believe the former but not the latter. They seem pretty parallel to me though, so I'd be curious what you thought the differences were.
[2] You could disagree with this too and simply be a lassez-faire fundamentalist, but that would render your original question kind of pointless.