If they did treat every water bottle as an explosive, then yes, this procedure would make a lot more sense than evacuating the terminal.
So the bad guys will just find another way to get their precursors through security. TSA's focus on things just forces the bad guys to adapt; instead, it should focus on the bad guys themselves.
> This begs a number of questions
No, it doesn't. It may raise a number of questions, but that's very different than "begging the question", which is a philosophical term for a circular argument. Please stop misusing this phrase and contributing to the general decline in modern English usage.
I know it's fashionable to profess a relativist/descriptivist approach to grammar, but when people use words and idioms in ways inconsistent with their historical meanings, the language is degraded: it becomes more difficult to express ideas that could formerly be expressed quite simply and clearly. When I'm forced to say "That argument assumes as a premise the conclusion it intends to prove" instead of "That begs the question" communication efficiency and accuracy are diminished, and we all suffer for it.
We do not apply a descriptivist approach to our children's language use. If they misuse a word or phrase, we correct them, because we know that their misuse will disadvantage them in pursuing the goal of language, communication. We use a prescriptive approach in elementary school, in middle school, in high school, and in college. There is absolutely no reason why that same prescriptive approach, the one that preserves the utility of language and respects its goal, cannot continue to be used by the world at large. Fashion be damned! Leave your descriptivist ideology in the linguistics department. I care for communication, not ideology.