Ow, my dad :(

[National governance]

I have been discussing politics with my dad and both my parents are conservative republicans. We live in the US. But i'm an independent and whenever I breathe a breath of even the slightest defense of liberals my dad gets defensive and sort of yells at me. He watches Fox and never wants to shut up with his yelling and screaming, rhetoric at Obama. I consider myself neither conservative or liberal, but what can I say to him to avoid confrontation and tension. It's getting hard for me to shut up about my own opinions when my parents obviously watch the news every evening especially my dad. My mom can be more understanding. I seriously doubt my dad would give Obama a second thought or even do a generous deed for him. He yelled at me once the other day for me getting frustrated. So, why does he have a right to be angry and yell but I don't?