I hate the motto 'I guess we agree to disagree.' Why? Cuz it's a polite way to be a dick. It's a way to say, indirectly, 'I think you're wrong, you think I'm wrong, so let's ignore each other since neither will budge.' No-I'd rather say what I feel-you're fucking wrong, and I just don't want to deal with your shit anymore.
Learn to fucking speak your mind. Yes, be polite, but if ANYONE ever tries to have a superiority over you on any topic that deals with morality, and they want anything less than the best for every single human being, then fuck them-they don't respect their fellow man, they get no respect.