It's not an ad hominem, because the article isn't making an argument, and someone questioning his motives isn't saying he's wrong because of his motives.
Claiming "isn't saying he's wrong because of his motives" is just reinforcing what I'm trying to say.
Furthermore, no one is claiming the article is wrong because the author has ties to Gawker. The claim isn't, "Because the author has ties to Gawker, he is therefore wrong", the claim is, "Because he has ties to Gawker, his premises may be biased."
Also, you can't analyze the author's "arguments" because he doesn't provide one.