Please don't worry about offending me / invalidating what I say - it's an internet forum, I don't take it that seriously. Please take my response in the same frame of mind.
Your defenses... aren't.
It's not airing the letter to the general public that was problematic. It's thinking that those are appropriate things to say out loud that's a problem. One of my coworkers passed from cancer a few years back. Frankly, a lot of people thought he was a real jerk before he passed. Nobody said bad things about him to people who knew him after he passed. Not internally, not publicly, not part of the carpool, not anonymously on blind, not even as a little joke after having a few drinks at the bar. Speaking ill of the dead is nasty. And it's mean. People who liked the deceased will overhear you and they'll go home later and cry and think about what people would say about them if they died and then cry more. Mitchell (? I don't remember who tbh) kicked a puppy and put it on YouTube and you're here with "Yes, Mozilla has a long history of putting the things it does on YouTube." It's not the publicity that's the problem - it's kicking the puppy in the first place!
I'm not sure what I'm supposed to take from the CNET article. It wasn't really about gay marriage, it's because the board was indecisive and make a decision and then doubted themselves? So, it was just incompetent management? If you aren't sure about promoting somebody, don't promote them. Promoting somebody and then having them resign because you weren't sure is terrible. Mature corporations with competent leadership recognize that personnel decisions matter - that peoples' feeling are impacted when titles are granted and taken away - and make these decisions deliberately and carefully.
The Eich affair was the cause, but it's not the underlying problem. Mozilla lacks competent technical leadership. Managers with ten years experience in the product area who can make broad-lens decisions. You can see this everywhere. I participate in the web ecosystem in my day job. I'm always struck by the lack of professionalism in the emails from Mozilla employees on github issues. Most Mozilla employees mail like employees 1-2 years out of college. At my company, that fades - managers speak to employees who get too heated in emails and give them pointers with regard to staying on topic and staying technical. But you can also see them in product - Apple's Intelligent Tracking Prevention (ITP) feature - one of the most important strides for privacy on the web in decades - was produced by somebody with a 10 year lens - somebody who saw the security blog post in 2012 about being able to track Twitter users based on their image caches and who had dealt with a decade of the gigantic mess of incompatibility that is cookies for just as long. For their tracking prevention solution, Mozilla copied what some existing plugins did. And it all goes back to Eich. Because managers with 10 years of experience are closer to 40 than 20. They're substantially more likely to have seen political fashions swing - they've seen somebody (perhaps the Dixie Chicks) have their career ruined for reasons that seem incomprehensible a decade later. And they've accumulated at least one "unpopular" political view. And they've come to realize that some organizations are simply too interested in political fashion to be an appropriate home for them.
The point is - what happened to Brendan Eich doesn't prevent me from using Firefox. I don't use Firefox because it sucks. And it sucks because Mozilla can't hire good people with decades of experience. And Mozilla can't hire good people with decades of experience because of what happened to Brendan Eich (and the attitudes that led to it).