On the use of the term "ad hominem"

Buried deep in the comments to this post, Kelly James Clark writes in reply to Ingo Brigandt:

Ingo--I concede that Beckwith's response to Forest contained similar ad hominems. Read my response.

To which I replied: 

Kelly, my argument, which I think is shared by Ingo, is that neither Forrest nor Beckwith engage in "ad hominems." They give negative evaluations of the quality of each other's work. That is not an ad hominem.

Further, Forrest's examination of the claims made by others as to Beckwith's legal credentials is not an ad hominem directed at Beckwith.

And finally, our problem with Beckwith's negative evaluation of the quality of Forrest's work is his completely illegitimate recruitment of the EiC's disclaimer as backup for his evaluation. This is illegitimate on two counts: 1) the disclaimer does not mention Forrest; and 2) it does not mention the quality of any article, only tone.

In my opinion, it's fine for Beckwith to negatively evaluate Forrest's work. He can present his case for that evaluation. But it is wrong both philosophically and professionally for him to cite the EiC's disclaimer as support for his claims as to the poor quality of Forrest's article.

I have posted this separately as I think it is a very important point. Others are free to comment here as well.