Laws like this are a fantastic example of people trying to avoid a moral argument.

Whether or not chickens are of moral consequence is an argument that can be had; it is perfectly reasonable to for the owners of these factory farms to either argue that chickens are not of moral consequence and deserve no more protection or consideration than the rocks in a quarry or that the methods they use are moral and do not constitute an unreasonable mistreatment of the chickens.

But they prefer not to have that argument; this is not unlike many other industries who prefer to avoid moral arguments by hiding or denying the facts.