Since the other thread was closed before I got a chance to comment, I want to point out that Zdad correctly pointed out that he does not generally insult other posters (except one whom he called a troll). Although I frequently disagree with Zdad, and find his opinions to be biased and often based on misinformation, I try to keep my dialogue with him civil. I was very uncomfortable with the personal attacks, so I will take this opportunity to say that I think that it went overboard.
Wolf, an ad hominum argument is invalid (unless some of the force of the argument is appeal to authority) when the point being debated is not the person in question. I this case, the ad hominum argument, I think, was not being brought to prove the point about loshon hora. It was brought as a personal attack, to demonstrate Zdad’s inconsistency.
As an aside, LH does not apply to someone who is not “bichlal amisecha”, and IIRC, the issue of speaking badly about the deceased is not technically a LH issue. I could be wrong, but I think the problem with speaking negatively about Koch is that it shows a lack of hakaras hatov (appreciation) for what he accomplished on behalf of the Jewish people.