our lives are completely about risk.... from the minute you're conceived, there's a chance something will go wrong. As adults, we usually measure risk quite well... i don't know all the facts, but have seen drawings of the location of the McCanns room in relation to the restaurant/bar, and the different parents took it in turns to go and check on the kids. What they did is NOT something i would've done... but that said, you literally can't have one eye on your kids all the time... and if Maddie hadn't been taken, the McCann's actions would've meant nothing.
So it's the perpetrators that have turned this into something evil, not the McCanns. And as much as you try, you can't protect everyone all the time....
It's a bit like trying to secure your house, you can lock the door, put a chain on, get cctv, and an alarm, and a dog.... but if the crim wants in bad enough, they'll use a JCB !!!