As it often happens, I agree with Robert on this social matter. However, I think I also understand Ballmer's position.
If you do some research, you will probably find that 45% of Microsoft’s employees are fascists in one way or another. What about stakeholders? The Americans? Mexicans? Italians? Citizens of the world? You probably don't want to know!
On the other hand, countries only adopt policies when the need is perceived as significant in demographic terms. It usually takes too much time, and in the meanwhile you will have casualties. Companies only do it when even higher levels of consensus are reached.
Microsoft having a fairly complete anti-discriminatory policy is a great start. The fact that much of the matter is left to the individual in many countries is not so great, but it is to be expected, given the current state of the world.
That is not to say stop worrying and stop supporting gay rights, or any other often-discriminated group rights. On the contrary, it means what you say or do is even more important.
On a side note, and this is just my opinion, Robert's answer to the memo is very dramatic, but he missed the chance to ask Ballmer's for greater *personal* involvement in the matter.
Ballmer is saying that he and Gates would put their name on this, but they cannot put Microsoft’s name on this, because they don’t “own” every Microsoft “soul” out there, which is very right. Robert, I think this is a good chance. This is how leadership works sometimes.