I have included this test to just weed out hypocritical thinking.
The "certain" above is the problem, because it's hard to define: you cannot and must not isolate people from all consequences of their speech. Sometimes those consequences even come in the form of speech themselves (or something the Supremes would consider "speech"). I must have the right not to invite my mother-in-law to christmas when I just don't want to listen to her racist rants again all night.
On the other hand, there are some disproportional reaction that could create a problem for democracy. Lets say the top three mobile provides colluded to deny doing business with anyone donating to the green party. That's dangerous because those donations are probably not important enough for the individuals to stop using a phone, yet collectively they're enormously important for that democracy-thing we have going.
Similarly with employment: it cannot be right to fire a regular employee for their private opinions, as long as the employee does everything reasonable to keep them from interfering with life at the office.
Eich and Thiel are different in that their employment isn't quite as "regular". Firstly, "firing" is a lesser threat to them, because they have above-average chances of getting a different job (Eich), or the financial impact would be insignificant (Thiel). Secondly, their position in leadership makes their private actions more relevant to their businesses.