Well there's definitely some polarised opinions on here aren't there?
I think examples of large aircraft accidents in urban areas show that whilst there can be significant casualties on the ground, there are - more often than not - relatively few casualties on the ground compared to the lives lost on board. Contrast that to a scenario where aircraft are deliberately flown into large buildings.
So I'd respectively suggest that allowing an aircraft to crash into a packed stadium or a tower block would probably cause massively more casualties than an engagement.
That's not to say I would regard stopping such a scenario as a 'success' - it would obviously be a tragedy - but in the extremely unlikely event it was to happen I would view it as the least worst option. Utilitarian perhaps, but not IMHO 'preposterous'.