The point is valid, however, in the sense that the Shaido Aiel cracked well within a year, to the point where they would keep slaves, among other reprehensible and evil actions, despite the vast majority of their cultural institutions remaining intact. So why should anyone trust that another Aiel clan might not similarly break down? The Shaido were not exceptional.

And your point is valid as well; the Aiel don't keep slaves – they sell them to Shara. For being Cairhienin, or petty theft, or who knows what.