Religion is always potentially dodgy in a way that politics isn't.
Men and women of good will can discuss politics and at the end of the day it comes down to one's belief in what will and what won't work, it is in some fashion capable of being empirical, even if the systems it's applied to are too complex to easily prove that about. If you can prove that a particular way to achieve some generally accepted worthwhile political goal actually works - say eradicate poverty - then sane people will say "let's do that then" even if it is against a core tenet of their political philosophy.
On the other hand with religion there is always a risk that someone believes that you are genuinely bad if you don't agree to the same beliefs that they hold, that they are bad if they don't try and correct your disbelief, that god has told them so and that he/she/it will punish you for your disbelief and them for any lack of zeal. From there it kind of goes downhill with at one end you constantly being bombarded with pamphlets and at the other with roasting unbelievers over an open fire.
So, a little bit of politics, ish, sometimes, maybe. Religion, I prefer to pick and choose very carefully who I discuss religion with and where. I'm happy with anybody holding any religious beliefs they want as long as they return the favour and let everybody else hold whatever religious beliefs they want, including none of course. Because of the risk of the 'true believer' type outlined above it's safer to have an absolute bar on discussion of religion in some places.