Because that's part of the premise of a society governed in large part by the free market. That's an idea I support, but it only makes sense if market power isn't amoral. Tech company employees wield some of the most important power in our markets.
>"a society governed in large part by the free market"
I disagree and have a much more simple explanation. Activists naturally want to involve as many people as they can in their cause/struggle. By framing everything as political, they open up opportunities to proselytize in areas traditionally not appropriate for 'politics'.
If you couple that with a cultural expectation that people must take a side, and, that simply not being a [bad thing] is not enough, you must be actively anti-[bad thing], and you've got the current climate Brian Armstrong is trying to avoid.