When was it ever okay to discuss politics at work?
To make it against whatever workplace "rules" there are seems overbearing and thought-controlling. Our personal beliefs and political experiences make up a lot of who we are, our individual perspective on the world and somewhat how we think.
How can you hold your organization to socially responsible policies and actions if you can't discuss what should be socially acceptable? Political beliefs form the ideas of what is the scope of the organization's responsibility.
In my recent experiences at a hedge fund and a very large investment bank, politics were discussed pretty openly in both environments (alas this was only in NYC). I found the discussions worthwhile and informative as it helped me understand my own beliefs more.
It's unwise to hold beliefs that you never have to justify. You should put in the intellectual work so that you can articulate and argue your own politics it will make sure your beliefs are well founded.