Overtly political comments
They will come up. Politics and the government and the administration are all parts of our lives. To me, as long as it's civil, I don't mind the interchange. When someone throws out a hard right wing comment however, I reserve the right to respond to it.When people engage in name-calling or insults over political positions, that it beyond the pale - for me at least.
We get the same thing with overtly religious comments, with some believers bashing atheism, while some atheists bash religion and believers.
On any open forum, this is bound to happen - unfortunately.