My points are:
a) it seems that Meetup tried to optimise their culture for aspects that were not directly related to --and controversially, maybe even opposed to-- product excellence. i.e. their initial version of 'cultural excellence' was more about creating a pleasant inclusive place to work, rather than a productive or high-performing place to work.
b) further, if (as a result) your hiring decisions are more guided by prioritising people that will fit into and perpetuate that cultural vision, you're implicitly choosing to not prioritise hiring high-performers.
(As said before, it's not mutually exclusive - there may be some high-performers that do fit into your cultural vision... but on a macro scale, if you follow that particular cultural vision, the trend will be away from excellence and performance.)