You’re playing very fast and loose with what constitutes an ad hominem. This ain’t it. There’s some skepticism that an administrative tribunal focused on military grievances is going to return a legally sound decision on something that in large part is being argued on a human rights basis.
Administrative tribunals are interesting beasts. They’re useful and absolutely essential; they allow decision making of a quasi-judicial nature to be delegated to a body that focuses on a narrower and more technical field. The courts generally aren’t as technically informed on this, that or the other subject, so a great deal of deference is given to the decisions of administrative tribunals. Our system needs this. But, they’re at their best when operating most squarely within the arcs of their raison d’être. When a tribunal needs to stray from the technical into broader issues such as applying human rights considerations, they may struggle a bit to get things right, legally. This is why judicial review mechanisms exist.
It’s neither unfair nor reasonable for someone, seeing a tribunal making pretty weighty decisions, citing human rights grounds, when that is not normally its thing, and to question whether the tribunal members have sufficient expertise in that to consider the decision a solid one. Certainly not an ad hominem fallacy.