The paper was written by people with no training in the methodology, the result was that their methodology was very sloppy, and at this point scientists working

The paper was written by people with no training in the methodology, the result was that their methodology was very sloppy, and at this point scientists working in geology, archaeology, and related fields have shown that virtually every claim in the paper has serious methodological issues. It's not a coincidence. Pointing out initially that the people doing the work didn't have the training needed to practice the methodology isn't an ad hominem, it was a correct statement that we should be skeptical of their claims because they did not have the expertise or training needed to do methodologically sound science. In the end it's clear they didn't do methodologically sound science, and the initial calls for skepticism because of their lack of training were correct, regardless of "ad hominen" claims.