When did we learn about Ayers? In 2001 when he put out his book in which he declared himself to be unrepentant about his Weatherman days. That was long after Obama met him or had dealings with him.

In fact, he wrote a column declaring the same which by a joke of the gods was printed in the NYT on Sept 11th, 2001. That's when Ayers becames AYERS. Before that he was just another washed up sixties radical and plenty of people had dealings with him, including upstanding Republicans.