My favorite way to practice my writing these days is to attack one of their arguments and cover all my bases so they have nothing to attack. (It helps me keep plot holes in mind, or so I'm telling myself) When you present them with facts, and keep the conversation civil they have nothing to say. Oh, and the most important part is adopting a stance you know they won't argue against.
Personally, since it's true, I like to remind them that us on the left are also proud Americans and work from there. We love this country as much as they do. I also use my Christian card whenever applicable. Or when they say Black people would never have the opportunities they do in America, I just ask them if they've heard of the dozens of other countries where we have as many, if not more rights and opportunities .
Letting them know about where Q began really fries their system though.