Significantly less silly than allowing it to hit its target.
What people forget is that as far as AQ are concerned even a failed attempt is a win. It doesn't matter to them whether they pile into the Olympic Stadium or wipe out a housing estate being shot down.
What they are trying to do is to disrupt our normal way of life and looking at the security measures they are making a good start.
We have to assume that any and all threats are genuine as we can't afford a single failure. They can afford many failures.
Perhaps my memory is playing tricks but I seem to recall a more grown-up attitude during the IRA campaigns of the 70s/80s where we also had regular killings and bombings in London and elsewhere.