John McCain is an honorable man who is running an increasingly dishonorable campaign. Senator McCain knows full well that Senator Obama strongly supports and honors our troops, which is what makes this attack so disingenuous.
If in this campaign McCain would rise to whatever character it took to survive while he was held prisoner-of-war (a feat worthy of respect and honor but really has nothing to do with running a country) I believe he might sleep better at night. That ad is pretty reprehensible for someone who vowed to run a respectful campaign. And it's a shame whomever is driving doesn't think McCain can win without it.
Also? Kind of brilliant on the part of the Obama campaign. They've taken the man out of the machine both complimenting and scolding.
UPDATE: Chuck Hagel agrees with me that this ad is below McCain.