The presence of both motive and opportunity are not sufficient to prove guilt. In the same way, the ability to wipe out humanity and the removal of difficulty in doing so would not guarantee the eradication of humanity.
To assume that the absence of ethics in human subject research will result in hasty and notable advances in knowledge makes assumptions about what can be learned. It's very possible that even in the absence of ethics, many of the questions we have will remain unanswered for centuries to come.
The basis of medical science is to improve the lives of both individuals and humanity as a whole. If the method of study causes outright harm, then it has already disregarded its purpose and nullified possible improvement. It trades one health for another, rather than improving net health. Does harm
Remember folks, this premise isn't stating that morals and ethics aren't important, he's simply stating that we would've progressed further without them. And with that point out of the way, onto my because!
There are many documented cases throughout history of research halting because of ethics
An ethical framework that devalues individual human lives in favour of scientific progress to benefit the humans that remain is still an ethical framework, regardless of its compatibility with contemporary frameworks.