I say yes to controversial topics, because it will spread awareness on a subject that is not widely known, help issues that need to be fixed (but aren't because people are too sensitive to talk about anything these days i.e. being offensive about everything), and will also cause the general public to stop being so private about their opinions.
Actually, in my opinion I think that people are so easily offended that it just defeats the purpose of any intelligent conversation to be offered. It doesn't have to be politics or religion per se, but just controversial topics to compel people to open their minds to the world and not submit to any one way of thinking. I do not mean that a person is obligated to keep that conversation going if they feel uncomfortable, but it does give the individual several things to mull over and helps them become more open minded to the world.
Unless it is very offensive (racial or some such thing), I openly speak my mind. I find it refreshing to just debate/talk about controversial topics in an intelligent way rather than just skirting all intelligence and having a bland conversation. So many people are just interested on the latest gossip about celebrities and who is sleeping with who. No wonder the government, certain scientific communities (i.E. The pharmaceutical companies), and other organizations are able to get away with such surprising atrocities!! Open your eyes people and stop shutting your mouth (unless its just going to be an ignorant slur). So yes, controversial conversations are fine to be talked about in public and I find it hilarious that it's "impolite" to talk about such things. But there are general social guidelines; there is always a place and time for such conversations and then there are times where it is just inappropriate (a wedding for example).
I don't mean that it's okay to push your opinions down another person's throat, but it to speak about it in such a way where it is thought provoking and open minded to all possibilities.