There isn't anything in there about "employees publicly speak out". Some board members (not employees) stepped down but IIRC they did not actually speak out and call for Brendan to resign.
Everyone on that list worked for the Mozilla Foundation, and would not have reported to Brendan as CEO of the Mozilla Corporation (which made that tweet misleading at best). I referred to that group already in the comments here.
AFAIK no Mozilla Corporation employees spoke out publicly in this manner, and internally I did not hear any such sentiments from Corporation employees. On the contrary, a lot of Corp employees expressed anger at that Foundation group ... not because they supported Brendan's Prop 8 position, but because that Foundation group poured fuel onto a fire that was doing great harm to Mozilla.
https://arstechnica.com/information-technology/2014/03/mozil...