One counterexample is supposed to knock over a theory. Black swans are so iconic that counterexamples are called a black swan events

You’d think that the “lean mass hyper responder” studies that showed that high fat diets do not cause heart disease, that high LDL is not associated with heart disease, yet it is still standard to treat LDL in the hope it will prevent a heart attack

If the consensus on a hypothesis doesn’t change when facing a contradiction, then whatever those people are doing is not science.