First up, let me say this - I agree with Rob Pardo that Blizzard should be focusing on epic entertainment experiences, and I have no difficulty with their desire to position themselves as a developer who focuses on gameplay and fun over narrative. And I think it's laudable that Rob himself seems to understand that this can sometimes backfire, as he said in the speech.
No, my objection is a purely pragmatic one -- I believe it's actually easier to be diverse in how you populate your game world than to not be, and that the lack of diversity ultimately damages that fun gameplay for a sizable chunk of your player base. To use just one example, we know that women make up almost half of people playing these games. Including characters that are women in positions of prominence (as just one example) invests women more fully in your game experience. It benefits you, because it enlists them as allies towards the ultimate goal of creating those fun, epic experiences - and the respect the article mentions? It cements that respect. If you want to have a reputation, it helps to enlist the players, to make them do the work.
Especially if your focus is on fun, rather than narrative, this is a decision that costs you nothing and reaps you rewards. The same fervor that can turn to ire and negative media attention can be made your ally - the inclusion of prominent characters that say that women (for example) are welcome and valued enlists women as participants. You can't have fun gameplay without players, and those players will do the work of promoting and proselytizing your work.