I wouldn't work for Mozilla if he was the CEO. I doubt they care about that specifically, but a lot of other developers probably feel the same. Good luck hiring any gay people. Employees were in revolt, one went on strike, etc.
His donation has been well known for years, and Mozilla has had no apparent problem hiring or keeping gay developers even through he held an executive position and had massive influence there. Given that, and the fact that there have been gay Mozilla employees who supported his appointment to CEO, it seems unlikely that Mozilla would no longer be able to attract gay people.