He hasn't attacked the man because he hopes in avoiding that area he won't be attacked himself for the things he really doesn't want to own up to.
It just doesn't work that way.
Also, McCain doesn't have the record that Obama has for hanging with the wrong crowd.

* Jim Hensley, Convicted Felon
* G. Gordon Liddy, Convicted Felon
* Charles Keating, Convicted Felon
* Raffaello Follieri, Convicted Felon
* Rick Renzi, Under Indictment
* Rick Davis, Freddie Mac Lobbyist
* Charles Black, Lobbyist for Dictators
* Richard Quinn, White Supremist
* Pastor John Hagee, Bigot
* Pastor Rod Parsley, Bigot
* Todd Palin, Member of Secessionist Group
* Andrew McCain, Resigned Manager Savings & Loan
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