It's best not to try to quibble with rules unless you like to be hassled. There are plenty of rules and that make no sense. You can take bottles or other reasonably heavy glass objects which can be converted to a much better weapon than a pocket knife in one second. Most airports have made it impossible to park near the building, but there are thousands of people waiting to get through security checkpoints so you'd think the bad guys might just opt to detonate something right before anyone gets checked at all.

CO2, lighter fluid, and the like is not allowed, but aerosol toiletries are. If you've ever screwed around enough to make a can of hair spray or deodorant explode, you know it's not something you want to happen on a plane.

The list of strange rules is nearly endless, but most of them are fairly clear. If you try to board with things that are specifically prohibited, you'll eventually get in trouble. If you need some sort of rationalization, just remember that the purpose of a rule is typically to reduce a particular kind of problem, not eliminate it outright. In the real world, 100% solutions rarely exist.