That still doesn't answer the question. Your response seems to suggest, as did Luigi's, that the organizers should have made a conscious effort to include women and minorities on the panel. The question is, why?
This is why I (sadly) consider myself a feminist -- we're still far away from equal opportunity -- where making an effort to overcome cultural bias in the form of sexism isn't needed. The number of commenters here and on the linked article that assume that a selection that includes only white males, clearly must be the correct one filled with all the most qualified speakers from England illustrates this point.
I'm not really supporting the idea of shutting down the conference over this -- I do see why someone might have raised the issue on Twitter. I don't quite see how it could (reasonably) go from there to cancellation of the event.
This sounds a lot like a tempest in a teapot to me -- the real issue seems to be that their sponsors were spineless twats. But then again, that seems to be what you get for trusting the invisible hand to help you get things done.
I'm not saying that diversity has no value, or that the speakers were the best possible speakers who just happened to be white men. I'm saying that, if you're going to claim that the speakers should be diverse, you need to justify that claim. Is it better to have diversity in speakers than the most technical accumen, or is it your argument that the best group of speakers will likely be diverse? What about when they're not? Why is diversity important?
Now, for what it's worth, I believe the best group of speakers probably would be diverse, but only by virtue of the racial and gender composition of the set of experts, not because diversity itself has any significant value in this case. That the selected speakers were white men may be evidence of a suboptimal selection process, or it may be simply a statistical anomaly. What it isn't, is a problem in its own right.
What evidence? If they choose speaker based on purely technical factor and ended up with all white-male, why must they change the result?
You're right though that we have no real evidence for this, this is just a natural assumption to make given the evidence we do have (the lineup).
As a poster said above me, this could have possibly been mitigated by publishing who they considered and possibly even selected that were non-white/male and couldn't make it. (this would give us some of the evidence you mention).