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.