The reason he couldn't answer is because his supporters, the right wing Christians, do want to be able to fire LGBT for no other reason than their sexuality or gender identity.
Of course they, being the righteous ones, do not see that as discrimination at all. To them it's freedom of association or the free market at work. Nevertheless it is in fact discrimination. It is unfortunate but their minds are so thoroughly occluded by their dogmas that they have truly list the ability to distinguish between right and wrong.
And if someone thinks I am being simply anti-Christian about this, go read their forums sometimes. Although you will need to steel yourself against some real nastiness, they talk about this very thing all the time.
There will be no compromise with these people. There can only be their, or our, defeat. Which will it be?
Sapere Aude