By "self inflicted", they aren't claiming that Kerry deliberately wounded himself, such as shooting himself in the foot. The claim is that Kerry's first injury came from him firing off an M-79 grenade launcher at a nearby target and getting hit by a piece of the shrapnel from the blast.

A Purple Heart is supposed to be given for a wound suffered in combat. Under that guideline, Kerry's wound by his own shrapnel could qualify for a Purple Heart if he was in combat when injured. I have not confirmed it yet, but supposedly his book "Tour of Duty" may undermine his claim that he was under fire at the time. Supposedly, several days after this wound, he wrote in his dairy (the basis for the book) that they were all in good spirits because they had not come under fire yet. If that claim is true, then his first Purple Heart wasn't deserved.

I'm hesitant to buy a copy of "Tour of Duty" to check this particular claim, but I just might get a copy of it and the "Unfit for Command" book to compare them side by side.