From the NY Times article.
"A doctor, Louis Letson, repeats accusations he made in newspaper interviews this spring that Mr. Kerry did not deserve his first Purple Heart because his wounds resulted from a ricochet off friendly fire, saying in the advertisement, 'I know John Kerry is lying about his first Purple Heart because I treated him for that injury.' The Kerry campaign pointed out yesterday, as it had previously, that another doctor, J. C. Carreon, signed Mr. Kerry's treatment record.
Mr. Hoffman said the group was spending $500,000 to run the advertisement but would not say how long it would be on the air; a Kerry aide said the buy was far smaller, $156,000 in seven smallish markets like Green Bay, Wis., and Toledo, Ohio, suggesting it was a 'vanity buy'' intended to attract news coverage."
This ad is the same discredited tactic used to smear John McCain in 2000 done by many of the same people. Their statements have been effectively countered before but that doesn't faze them. As someone famous tried to say, "Fool me once...."