Bill Ayers is was a member of the Weather Underground, a group responsible for many bombings forty years ago , including one at the pentagon. Before the Weather Undergroung, he was the leader of a non-militant group called the Students for a Democratic Society.
The WU were a confused bunch of left-wing activist that evolved from the SDS. The WU had noble ideas that they tried to accomplish using foolish tactics. Protesting the Vietnam war by bombing government buildings is no way to accomplish anything. Bill Ayers was part of this group and is not exempt from these attacks.
After these attacks, Bill Ayers became an elementary education activist. His recent work is for a noble cause, a cause that he recruited Obama to help him with.
The sound bite, "We didn't do enough" is a statement grossly taken out of context. This statement was a response to a question about his involvement in protesting the Vietnam war. The soundbite we all have heard many times is a complete distortion of Bill Ayers' position. In fact, he wrote a letter to a city lawyer (Richard Elrod) injured in an attack made by the weatherman to express his condolences. The lawyer is quoted as saying that Bill Ayers was "Remorseful".
We know Obama and Ayers knew each other more than Obama expressed to at first. If Obama is going to be attacked, attack him here for not being completely honest. Don't attack him for knowing this man, in fact, Obama said his actions in the WU were dispicable. They were on a board together to improve the community, not to blow things up.