It's hard for people having discussions about sensitive subjects (another way of saying "something actually important") to develop proper etiquette when the opportunity to practice such discussions rarely arise. I don't mean to pick on you specifically, so please don't take offense at the example, but I get the feeling if you and your friends regularly had discussions regarding your political views, it would be much easier to establish level headed discussions, than rare conversations where emotions just boil over the top.
That may be true in some cases, but the bottom line is that I know a lot of people that develop such overly dogmatic views fueled by their culture, social circle, and cable news that it really is impossible to have any civil discussion with them. Some people just aren't willing to concede that they might be wrong about anything, and they will relentlessly defend those views.
Maybe things would be better if those people did start debating and discussing these issues at a younger age, and they had a good example to follow for how to properly have those discussions (i.e. teachers, parents, etc...anything except cable news).