As someone with some experience dealing with this, having learned how difficult it is to fix I would reply something like "You are wrong. If you want to learn WHY you're wrong, tell me and we can work on this together. Otherwise, I'm going to go now."

Playing the game a bit: "Okay, bear with me a moment, this is going to sound a little odd.

I'm not sure what you mean by "outside the realm of causal processes". Does that mean it happens on its own, with no outside influence at all? Nothing causes it, it just... Happens? Even if it's a 'magic' skill, shouldn't he be the one to activate it? I mean, worst case scenario, it's caused by someone drawing a card from a deck. It doesn't happen completely independently of reality, it's CAUSED by something. If your cousin is the only one with this power, I'm sure he could be studied by the scientists and they could figure out what lights up in his brain as he does it.

A minor note, I was once a card magician, and there are very specific ways to either force people to choose the card you want, or to figure out what card they've chosen. I can show you a few, if you want.

Next, 'communing with the entire universe' is a pretty arrogant thing to say, isn't it? I never got any communication, anyway. Question for you - how would it feel to look deeply inwards, ask 'the universe' questions, and receive answers from your own mind? Would it feel much different from what you feel now? Usually it's better to assume that confusing or 'unexplained' things are happening in your mind, not in reality. You FEEL like the universe has told you that he loves you, but that would look exactly the same as if it was just your unconscious mind telling you. How often have people said that they were deeply, permanently in love, but then it didn't work out? Do you really think you're that much better than everyone else?"