It's as simple as this:
I disagree that all bomb 'threats'- real or not, credible or not- need to be treated exactly the same. We have brains. Zero tolerance policies lead to outright stupidity, as we've admitted in other threads. There are millions of these type of bomb 'threats' every day. It's too expensive to assume all those people are terrorists.
Maybe you catch one terrorist who makes an ill-advised apparently innocent joke at the wrong moment- I don't know that's it ever happened, but it's conceivable. But that comes at the cost of a police state.