We don't talk about politics or religion at work for the same reason that we use money instead of barter.
If we only used barter we could only trade when we could find matching goods/services between trading partners, by using money instead we avoid the matching.
If you discuss politics at work you risk a situation where some people cannot work together because of incompatible views which are essentially irrelevant to the work being performed.
On the contrary: Politics have to be discussed at work because that's where "incompatible" people meet. Discussing politics with those who share your views isn't all that enlightning.
The work being performed is generally completely irrelevant compared to politics so it has to take a backseat. The capitalist will just have to deal with the fact that their workers are not mindless unpolitical drones.
That might be good for political discourse, but it's not good for commerce.
And if someone has a weaker position in the workforce it may not be good for their financial welfare: No one has to just deal with someone they can fire. How much is political discourse improved by communication in the context of that kind of asymmetry?
