You will not find the clip on youtube where Louis CK elaborates on the subject, but he discussed it in a clip in Season 2 of his show Louie (Episode: Moving). Since youtube does not allow it to be uploaded, here is a transcription:
And we used to let kings take over for their fathers. That's the craziest rule that ever existed, that if the king dies, they let his kid be the king. What are the odds that he's not gonna be a piece of shit? How do you let that... That's one of the weirdest things that we've ever done as a race of people, I mean all of us. White people... I mean, there are black kings too... African countries. There's never been a black king of england. That's never gonna happen. That's one colour line that's never gonna get... Don't even hope, man. It ain't gonna happen. There's not gonna be a black king of england. I mean, after all that white that's been pumped into their blood for years, they've just been this kind of jizzy white colour for all these generations... Purply... They're all... Every british royal looks like cockmeat. That's what their faces look like, an Irish penis. That's what they look like, someone took an Irishman's penis and stretched it out and drew a face on it with sharpie. [makes face] Just... That's what they look like.
Comedian Louis CK frequently manages to be very funny as well as topical. He's the only person I know of that put rumsfeld on record for being unable to deny being a lizard.
PS: Why do the english royals all look like they're made of cockmeat? As comedian Eddie Izzard points out: "cos it's a bad idea when cousins marry."