With the benefit of hindsight, yes.
If I were working at Mozilla it wouldn't affect how I'd act in the future though. Yes this turned out very poorly. But you can't predict these things. And principles are worthwhile to speak out for. And we don't even know if he'd have done a better job (though this is admittedly not hard)
Eich wouldn't have made a change to prop 8, no. But the culture at and image of Mozilla would have changed.