Here is an oldie but goodie. Carl Sagan explains Time Dilation.
Carl Sagan Explains Time Dilation [Video]
Not too long ago I was discussing naturalistic evolution with an atheist. After a while of being unable to convince me of its truth, he told me that if I understood it, I would believe it. And further that since I didn't believe it or understand it, that any arguments I offered would be strawmen, and he didn't have to respond to them. I let the discussion rest at that point. Not because I saw the problem with what he was saying, but more because I was caught "off guard" and saw that he had actually come to that conclusion before we even began the conversation.
I wasn't too worried about it at the time, but I've come across similar claims from those who don't agree with me on other things as well. So I'm going to take a few minutes to put together a response for such claims.