The message this decision says is "We care more about our Ill-informed opinions concerning a popular hobby than about our stated mission of helping children." Nobody is asking them to play the game, or support it, or even say anything about it.
Their story about "We are selective about what we endorse" is sheer bull. An Endorsement or a Sponsership is when one person or organization lends support to another, in this case they are not Endorsing or Sponsering Gencon, Gencon is lending publicity and financial assistance to them. It's not even a "You give me a dollar today and I'll give you five bucks next week" thing, its' "Here, Take five bucks, please."