I too was admonished not to talk about politics and religion, but not by my father. Instead it was "polite society" that made that request of me. Growing up, as I watched my father carefully speak his mind, write letters to the editor of the local paper, and stand up for what he believes in, I learned that if we don't talk about these things openly and honestly then we will never change the status quo and we will simply be the sheeple that the corrupt power seekers want so desperately for us to be. So, I learned when someone says "Don't rock the boat" to respond "Why the hell not?" If they can give me a good reason that's not rooted in shame, then I will. Otherwise its open season on any topic.
HA..because you have folks, most of who are like me, who try and keep it unemotional, but when our value systems are questioned, each one of us usually becomes defensive in some manner. You have to address the issues, yes, but more than that, you have to keep emotion to a minimum if you can. That is what you saw from your father. I find that hard to do sometimes which makes me feel bad later, as I do not dislike anyone for their opinion, even tho in the heat of the moment I would love to knock some sense into them, as if that would work.