It's always entertaining when Silicon Valley companies learn that hundred-plus year companies have these stiff adult things called "rules" around for a reason. I can't imagine seriously engaging in significant political discussion at work, and can't imagine a positive outcome to it.
Well, when a company actively tries to make its employees private life a service provided by the company, that's inevitably going to include their activism as well.
The bigger companies in particular are your employer, your restaurant, your gym, your laundry service, your transportation, your social life...
It's easy when you've made sure the entire company leans the same way though. It would be odd to be a right-winger and work in Google--knowing that they're doing everything they can to hurt me. But of course money is money and everybody has a price.
I'm a right-winger in a leftist workplace. The key is just to keep your head down whenever politics comes up, and never participate in discussion about controversial topics. Generally I would act the same in a right-leaning atmosphere if one ever existed anyway, but at least then I wouldn't hear my coworkers' rants.