This is pretty strange to me. I've worked in a bunch of very different places, including Intel Corp. and also defense contractors and US government installations, and people generally stayed away from political discussions unless they were around people they already knew were like-minded. The only place I saw political discussion turn really sour was at Intel when we had a contractor who was extremely religious and conservative, and would talk publicly about how homosexuals "offended" him, etc. We ended up not renewing his contract because he was toxic.
At government places, political discussions were generally avoided. The Hatch Act might have something to do with that (it's illegal to campaign for any political candidate at a Federal workplace), but mostly I think people just had good common sense. They did talk a little among themselves in the run-up to the election, but it was in-person, with a buddy, not meant to be a public discussion.
What's really shocking to me here is this revelation that there's actually "global mailing lists" within the company where political talk is happening. This, I cannot imagine ever seeing at any of my prior employers, ever. I honestly can't imagine why any company would tolerate such a use of its equipment this way. It's just a recipe for trouble.