The purpose of putting people on stage is not always to showcase just the best, but often to showcase different viewpoints and different ideas.
Promoting just the "best" from the viewpoint of a single background - now that is arrogant and harmful because it assumes you actually know best. If Mike always knew who was best to promote, he'd be a billionaire and every company he invested on would have people everywhere throwing money at them.
As such, especially for something like Techcrunch Disrupt, it is valuable to promote a diverse group - whether based on race, socioeconomics, geography, gender - especially if a group is severely underrepresented - to get a wider view and perhaps learn something from it.
If anything, a great deal of hidden racism is a direct result of people insisting on picking what they think is "best" without taking into account the hidden biases brought by their upbringing, school background etc. and never being exposed to a more diverse set of views.