Doesn't that make the speaker lineup even more peculiar?
1) It's a process. We already have non-white people in top positions (both in the industry and in academia), so there's no lack of inspiration, but it takes time for those who have inspired to make their way through school and immigration. Right now there are multitudes of Indian and Chinese students in American universities: in a few years you'll see them at conferences. And that is already going to happen: they're certainly not going to drop out of their degrees and go home because some Brits were not diverse enough with their conference in Manchester.
2) From what I've seen, many of those students are more interested in enterprise or research applications than in doing web development with Ruby, so you might see them at slightly different conferences.
3) This particular conference was in the UK, not in America or in India or in China or in France. Let's be careful not to call the entire country racist just because it's mostly populated by whites.
I agree with #2, but Ruby is a fairly special case, in that its creator, and still one of its main contributors, is Japanese. So you can't make the argument "if only non-whites stepped it up in Ruby dev"...(but the argument that none of the Japanese speakers could make it/were affordable/wanted to come is still legit).
It's true that Ruby is a Japanese invention (I wonder if all these racists are aware of what they're bringing into their good ol' boys' club ;)), but as you note, Japan is so far away that there are still difficulties in participating in a little new conference in Manchester. Also, Ruby got its big break with Rails, which was developed in Chicago, I think, so the Japanese community might not have gotten as much of a headstart as one would expect. Or maybe they are using Ruby for far more interesting things than web development. I don't know.
And I think that's the heart of the matter...The Japanese (or any number of non-European/American Ruby communities) could be doing something amazing...and we would have a hard time knowing, because of the inherent geographical and language barriers. That's why it's not just the "moral" thing to make an effort toward diversity, but it is a potential creative and intellectual boon.
In any case, the OP should've just included a statement saying, "we asked speakers x,y,z, for example, but each had a previous commitment, etc. etc. etc.". In fact, that's a point they should've made more prominently in the debate before canceling the conference.
"so there's no lack of inspiration" --> Really, can you point to the numbers?
It's cool. Everything is totally cool.
I haven't had a boss who wasn't a white male in nearly a decade, women are still harassed at conferences, and we can only find white guys to talk at a conference about a language invented by a Japanese guy.
But Camillo's class has foreigners in it, so everything is completely okay now.
There's a big difference between the composition of your university class and the social makeup of a professional community. Let's talk when you're out in your career.