This lack of consistency only shows that these security controls have little to do with actually ensuring security of the flight.

This is a mechanism of scaring people into obedience. So that they feel like criminals when passing through. 

0xIlmari

Other people on the thread suggested that security might have thought it would be some kind of club-like tool.

I just had a butter knife confiscated at an airport security. Butter knife, no edge, no point, a regular butter knife. And it was right as I was rushing to get to a next flight, I didn't try to protest. It really pissed me off.

I've had small size swiss army knives get through lots of times, and also get confiscated a couple times.

If something is iffy, I find it's best for it to have a confusing, non-knife like shape. Like for instance - folding scissors. I've always had these go through, even though it's just as dangerous (if you wanted it to be) as any knife with a 2 inch blade, but the knife will definitely be confiscated, and so far the scissors have been okay. 