Earlier quoted context omitted.
I certainly agree that it's ethical. As far as practicality goes, demanding payment will invariably amount to refusing the review assignment. I don't have any problem with that, but I don't believe that any publishers will be willing to meet such a demand.
Can you explain to me why academics will spend their time reviewing journals without the expectation of getting paid? I would never accept work where they weren't planning on paying me
Publishers have simply managed to externalize the cost of reviews (and authorship) to universities, i.e. to students in the case of private university, and to students and states in the case of public ones.