Yeah, same here. I couldn't find the entire thing online either. I may as well just paraphrase it, because it's hilarious.
So, Tim Minchin is trying to prove that his wife has a darker sense of humour than he does (he's always taking the piss out of her on stage and people wonder why she puts up with it). So he describes a situation where they're snuggled up on the sofa watching a movie, their 4 month old baby is asleep upstairs. Part way through the movie, Tim says "darling, I'm going to go check on the baby" as he moves to get up. "No, don't" his wife replies. "I mean, if you get up and go in to the room, the light will just wake her up and she'll take ages to settle again and we'll be up for hours." She pauses "and if she's dead, well, there's not much we can do about it is there? So we may as well have this last moment of happiness before our lives collapse around us."
It gets worse/better (depending on your opinion).
The kid is now a bit older. They're out in the park one day when, as kids do, she picks a penny off the ground and sticks it in her mouth - naturally, parents don't like this. Tim is going on at her "no sweetie, please, spit it out. It's dirty, you don't want that in your mouth. Your mouth is for food, and when you're older, ****."
His wife looks at him apparently furious. "Tim! You can't say that to her! What if she prefers pussy?"
And lo, the man is a fucking legend.