What was your first reaction back in May when you heard of plans to build a mega-mosque near the site of the Twin Towers in New York? Did you assume it was a tasteless joke? Did your jaw drop? Or did you think: "What a good idea. No better place."

My bet would be that most readers (including self-described liberal readers) had a touch more of the former reaction than the latter. Some people even said so at the time. A number of families of 9/11 victims spoke out against the building and for a few weeks the idea of a 13-storey mosque complex beside the World Trade Centre craters, due to cost £68 million yet with no known financial backer, seemed a dead duck.

So how was it that within a few months many of those same people, most notably the most loudly self-declared liberals, were not merely advocating the building of that same mosque but in many cases seemed eager to build it themselves, finally depicting its construction as the sine qua non of America's survival? The distance between first and second instincts is always illuminating. But this one turns out to be more than usually so. Public debates in America tend to happen rougher, faster and more ferociously than they do in most of Europe. And so it was that a heated debate over one hot summer transformed a planning dispute into something far larger and more significant.

Daisy Khan: Wife of the Imam of the proposed Ground Zero mosque has claimed to be a victim 

It was at the beginning of August that the Mayor of New York City Michael Bloomberg stood with the Statue of Liberty in the background to make a major announcement. The planning regulations surrounding the former Burlington Coat Factory on 45-51 Park Place, had already met opposition at the community board advisory level. National polls suggested that a majority of Americans were opposed to the building of what was then called Cordoba House, a couple of blocks from Ground Zero. But Bloomberg thought differently. Surrounded by the requisite collective of religiously-attired figures, Bloomberg declared that restrictive planning laws of New York would not be allowed to stand in the way of the planned mosque. The debate was not about a planning application any longer. It was about something more, he declared. It was about America.

In his often teary-eyed speech, Bloomberg exercised the now decade-long tendency to believe that al-Qaeda meant whatever you want them to have meant when they destroyed the Twin Towers. Bloomberg declared: "Three thousand people were killed because some murderous fanatics didn't want us to enjoy the freedom to profess our own faiths, to speak our own minds, to follow our own dreams and to live our own lives." The issue, he said, was "as important  a test of the separation of church and state as we may see in our lifetime". And it wasn't a test he intended to fail. Expressing his support for the construction of the mosque, he said: "The community centre and mosque will add to the life and vitality of the neighbourhood and the entire city."