I think the media attention in the beginning is partly what led to the tide of opinion turning against the McCanns. Not just in terms of those who questioned their potential involvement but in general.
In the beginning there was much talk of how Madeleine could be anywhere and how people needed to look out for her. Talk of the blemish in her eye, and some crackpot theory that she'd been taken and was essentially just somewhere out there in the world.
The result of this was that people were being stopped in the street, questioned as to the parentage of their own children etc, there were even numerous posts on MN from people who either had been stared at by someone who believed their child might be Madeleine. And conversely,posts from people saying that they'd seen a child who looked like Madeleine and should they act, followed by the inevitable "of course you should, you would never forgive yourself if it is her." Honestly the reaction was hysterical in the extreme and far, far beyond the realms of a normal missing person search.
Of course Madeleine wasn't going to be in your local shopping/garden centre. The very idea that people were encouraged to go down this route was ridiculous in the extreme, but it was as if people had been gripped by some kind of Madeleine fever and IMO wanted to be the one who found her.
But it did mean that people started to think more rationally about it all, and started to resent the implication that the search for one child should take precedence over everything else in the world.
The abduction theory should never have been touted as a possibility any more than the theory that the McCanns kept Madeleine in a freezer for three weeks until they could drive over the border to Spain.