Let's put aside for one moment 'how' the Rove presentation came into their hands. And let's not worry about whether the presentation was a plant or real. For they thought it was real and that is what counts.
Obviously Kerry was involved. Matter of fact, there were several articles out there about this meeting and there is no dispute that Kerry was involved.
Why isn't Kerry held responsible for allowing unauthorized people to review this presentation?
For the same reason that Sandy Scissorhands just got a slap on the wrist for stuffing documents in his underoos.