He didn't say it around the water cooler; doesn't that make all the difference? He said it three years ago semi-publicly but away from work, deleted it years ago, and has put some plausible effort into moving away from the viewpoint people took offense with. In your world, we're not allowed to make political/social mistakes off the job 3 years ago, even if we change our mind afterward?!
> These employers have the same right to associate with whomever they choose... Making everyone work in close company with folks they aren't comfortable associating with.
I have to believe they interviewed him pretty well and liked him just fine the way he is today and in person. What evidence do you have that anyone he worked with was personally uncomfortable with him? It looks like what happened is, the mobs/journalists dug up reasons to hate his 3-years-ago Facebook persona, and Twitter exercised that "right" so they could save face.
If we apply your apparent rules fairly, even Adria Richards will get fired for her own variety of "dongle" joke[1] on social media literally during that same infamous PyCon[2] 3 years ago.
[1] https://twitter.com/adriarichards/status/312265091791847425 For posterity, someone tweeted "I made it to US and A. I've received my traditional TSA welcoming - having my nuts fondled." and she responded "you should put something in your pants next time...like a bunch of socks inside one...large...sock. TSA agent faint"
[2] https://twitter.com/adriarichards/status/312265576896679937 "OMG! you have me blushing here at PyCon!"
P.S. SJW tip: trawl those threads for anyone remotely high-profile who challenged her, so you can get them fired for misogyny or something.