Regardless of the actual numbers (I have no idea what they are), I wouldn't expect the CEO of Reddit to effectively announce to prospective advertisers that their user base was a bunch of racists.

Her actual claim was that the people who are critical of her and the changes Reddit made are a minority. For example, http://www.nbcnews.com/news/asian-america/reddit-users-turn-... and http://www.nytimes.com/2015/07/04/technology/reddit-moderato... for example.

Being a racist or mysogynist is unrelated to being critical of or disagreeing with how she was managing Reddit as a business.