I think there are two situations in which you might see this kind of rebuttal: 1) The reviewers were truly unreasonable, and the authors feel they have no hope

I think there are two situations in which you might see this kind of rebuttal: 1) The reviewers were truly unreasonable, and the authors feel they have no hope of winning them over. Instead, they try to highlight the flaws in the reviews to play to the Area Chair, and hope the reviewers are overruled. It's a longshot, but worth a try if you don't feel there's another path. 2) The authors aren't really familiar with the review process, and are just upset with the negative feedback. They're just looking to argue for the sake of arguing, and not as part of a strategy to get accepted. I think that's what we're seeing here.