When you write a memo and distribute it to a group as large as he did you can bet that it will go much further and in fact the usual goal of writing such memos is to aim for widespread distribution.
So, tip for future memo writers: stay in control of the narrative. That's easier said than done.
> Is it still fair to fire the original author?
That's a moot point, companies do not like political activism within their ranks whether or not it spreads to the outside world and affects the image of the company in a negative way or not. But when and if it does you can be pretty sure heads will roll.
Second tip: If you do wish to write that memo try to get buy-in from your higher ups (and in writing) before releasing your memo to your peers.
Third tip: don't do it. Unless your position is absolutely ironclad and you don't care about your future employment writing memos will probably not make a difference in a positive way and there is plenty of downside with the memo writer holding the bag in almost all cases, especially when such memos target controversial subjects, they will almost certainly end up being used for political football.
He didn't widely share his memo. Someone else inside Google leaked it to Gizmodo, which widely misrepresented it and started this shitstorm.
Who gets the blame in such scenarios? Is it still fair to fire the original author?