This seems like a perfect example of the intellectual dishonesty k2enemy was talking about. Those two examples are not comparable.

There is no demonstrable, rational connection in your example. It is entirely rational and possible that extra airport security is a deterrent to airbourne terrorism.

"It is entirely rational and possible that extra airport security is a deterrent to airbourne terrorism."

Possible, but easily disproved. You can buy the material you need to make various weapons at duty-free shops, restaurants, and so forth on the other side of airport security. You can walk through security with a laptop, which has loads of sharp metal pieces, several lithium ion cells (containing dangerous chemicals that can be used in various ways), etc.

The 9/11 hijackers were not heavily armed. What I described above would have been sufficient for that attack, and the "extra" security at airports does nothing to stop that sort of thing.

Right. Your example sounds ridiculous because there is no logical connection between not stepping on a crack and your mother's life. To most people, there is a connection between airport scanners and airline safety. My point is that we should be stressing the fact that the scanners do not actually increase safety.