This is part and parcel of McCain's willingness to buy into the MSM's frame of reference on what lines of discussion are "appropriate" in this election. Someday, we may all look back in amazement that saying a candidate's full name was somehow declared off limits (would that have been the case if, for example, Obama's opponent had been named "John Goebbels McCain" or some such?).
But the fact is, that's what the GOP got when it selected John McCain as a candidate. He isn't really comfortable attacking his opponents; that's part of his famed "bipartisanship" that the press now cares nothing about. And he may simply have decided that maintaining his standing among the DC establishment -- where he will return, whether he wins or loses -- is more important than making a final effort to really win the election and warn the American people about what who Barack is and what he's comfortable with.
But whether he makes the case or not, what should be obvious is that there's nothing illegitimate in McCain pointing out that he's not attacking Barack's motives. It's perfectly fair to question the vision and the priorities of someone who could spend so much of his life in the company of so many people with hatefully anti-American outlooks. He can point out that the America that Reverend Wright and Bill Ayres apparently have seen and despised isn't the America he spent years in a rat-hole for defending.
And while he's at it, it would be interesting to know how much of one's income "the rich" need to give up in order to be paying their "fair share" in Barack's estimation.