One argument is just that the tests may yield false positives, particularly if the samples are mishandled or old.
In most cases, there's no doubt, though, so go ahead and ban them for life and claw back the money and cancel the results from the beginning of their competing. What a shame for Simpson, Montano and so many others to be deprived of their medals by cheaters and testosterone producers.
Looks like it was a bad meet for Russia (or maybe on the site they've already removed some of the banned cheaters?). But there's Semenya with a 1:55.45, pre-hormone treatment, winning by almost 2.5 seconds in the first year of competition.