Hello, Mozilla supports equality for all. We have employees with a wide diversity of views. Our culture of openness extends to encouraging staff and community to share their beliefs and opinions in public. This is meant to distinguish Mozilla from most organizations and hold us to a higher standard. We absolutely believe both in equality and freedom of speech. Sometimes standing for both at the same time can be hard. A CEO needs to be able to lead, and under the circumstances in the last week with the scrutiny over this issue, Brendan made a personal choice to step down from the role.

For some more detail on the subject you can also refer to some blog posts by Mozilla's employees:
https://medium.com/p/7645a4bf8a2
http://blog.gerv.net/2014/04/your-ire-is-misdirected/
http://planet.mozilla.org

I think you should be asking, what is wrong with the people who did the backlash towards Mozilla and Brendan when he moved from CTO to CEO.

It was known since 2011 that he made this donation in 2008.