The relevant question is not how common the test is.
The relevant question is, would it have made any difference?
Or, rather, what the chances are that it would make a difference, considering the fact that we live in a world where medical professionals (and the tools of their trade) are a finite resource that can be allocated in different ways -- some more effective, overall, than others. If routine PSA tests save 1 man out of 1,000,000, is it worth it? Maybe, it all depends on whether or not the time/resources of the physician could be better spent in other ways that might save more lives.
Most patients are going to want the most thorough care and will want to hold their doctor accountable if he doesn't catch something that the next guy would have, but there will always be a more careful doctor than yours. If you wanted to be super safe, you could get a thorough examination for all sorts of rare and common maladies every 3 months, but it'd be very time-consuming, inconvenient and expensive. Unless there's something in your medical history that calls for such frequent examinations, they would only offer only a negligible chance at improving your state of health compared to less frequent and thorough regular checkups.
Doctors are charged with the task of finding a responsible balance. It seems to me that if the doctor was acting in good faith, neither he nor his school should be held liable for the consequences suffered by an outlier -- at least not if there is strong evidence to suggest that, on average, his technique is more effective at treating patients and saving lives.