This has long since been covered. Think vaccine studies. Think REDUCE It where the study was carried out to term (they met required event/deaths rather than stop early when the results looked good). Think all the cancer studies where the study was stopped due to worse results for the treated group and that was always a possibility.... Volunteers get in harms way to advance knowledge, get free check ups, and a dollar or two of value. It's how it is done.
Almost every drug trial involves the risk that serious harm may result from being in the placebo group, at least compared to the drug group, assuming the drug works. Nobody is going to be harmed if their LDL-C goes from 75 to 82 for 4 weeks - hell, if it had been 82 to start with their docs would have been happy with that, it's still well within desired levels for at risk patients. It's not like you're feeding one group Round-Up as a placebo - MO is harmless and has been used for decades.