You and he are right that 'bioethicists hold back research'. Some research should be held back. So that part is true pretty much by definition. The article doe

You and he are right that 'bioethicists hold back research'. Some research should be held back. So that part is true pretty much by definition. The article doesn't use the phrase 'Mengele 2.0', nor does the original op-ed, though Pinker brings up 'Nazi atrocities' and 'armies of cloned Hitlers' and the author says 'no one needs an expert to verify that Dr. Mengele was a monster'. However, that's Godwining, and not testable. The question is more, will not listening to bioethicists lead to inhumane treatment? We know the answer to that is "yes." Look at the last few years of the American Psychological Association to see an example, where the board and the military secretly worked to change the ethical guidelines to permit practices that the APA as a whole found unethical, once it was revealed. Yes, it would be 'easy to make a prediction' for the two examples you suggested. Your original requirement though was 'testable predictions'. It would be unethical to run those experiments, and the point of bioethics is to block that sort of testing. Which means they are not testable. There are all sorts of experiments people might want to do if it weren't for ethics. How do you measure "worse outcomes"? Is it better to know the full natural progress of syphilis in a human, or to treat the human? If you can't measure it, it's not testable.