Avoid talking about something controversial is deemed self censoring by a lot of people here in HN.
You might be a forgiving person, but that is a gift not a necessity, and better not assuming people would return the favor. For more controversial stuff I choose to only talk with my inner circle which I assume I knew them well enough. The author makes the memo public to ALL employees, most of them he wouldn't even know their names. That is his freedom, however he should expect there will be reactions to his piece from them. And it is not really his business or within anybody's control to decide what reaction is appropriate or over the top at that point. This is internet, where things escalate proportional to the speed of light.
My understanding is that is that the guy shared this memo among a small group of friends at work using an internal forum specifically designed for this kind of discussion. If that's true, I hardly think it's fair to hold him accountable for the reactions of Googlers he never shared the text with, let alone those of the world at large once someone else leaked the memo to the internet.
As long as that person isn't constantly soliciting investment advice from me or asking me to front them loans, I don't think it's unreasonable for an adult to be expected to tolerate opinions that do not affect their work.
Hell, I've worked with co-workers who consider Jews illegitimate occupiers of their country, yet we still got along just fine by avoiding talking about politics in the break room.