Well, he was the navy liaison to the Senate for his last 4 years. He himself has termed it the beginning of the second part (read: elected representative) part of his public service.
Senate liaison (and admitted training as a politician) isn't exactly heat of the battle service.
That being said, questioning his military service is about like questioning Kerry's service: neither should be done. But Gillespie never said that what McCain did do before the final years of his service wasn't meritorious and heroic.
Oh, and ILoved, you forgot to mention that Gillespie himself was an Army Ranger. I think he's entitle to have his say on at least the traditions and perceived protocols of armed forces, agree with them or not.