I've seen something similar among mental workers. (Skilled software programmers.) There's this one "intense" guy who loves to hold forth about everything that interests him, including politics. So, one day, he pointed out that corporations are just out for themselves. Everyone laughed, until the manager said half-jokingly, "Not every corporation."
Then the other programmers laughed nervously and turned to their computers. The talkative programmer went on, but there was suddenly no one to listen, and soon he too turned to his computer.
When the manager isn't around, they're much more free to discuss worldly matters. For example, the last time the manager was absent, they engaged in heavy critique of intellectual property and corporations.
However, one of them avoided political disagreements like the plague. Some random hypotheses are:
* He's a good-natured guy who was punished for thinking very, very
differently. So he keeps his thoughts to himself and tries to be
happy.
* Leftists are often like some depressing doctor who gets a kick
out of telling you how terminal your cancer is, but isn't so
interested in sketching a real cure. The most rational solution
is to start ignoring him.
* Those of us who are very talkative -- I'm included -- are
frequently aggressive and bad at listening.
Tayssir