To be clear, it wasn't that he was "anti-gay" it was that he donated $1000 to Prop 8 in 2008, a California Proposition that made gay marriage illegal in CA until Obergefell struck it down 7 years later.

This is important because it is a clear delineation between "privately disagreeing but allowing individuals their freedom" and "actively campaigning to take away rights from Mozilla employees and users".