I would phrase it as "It's good we have a heterogenous open-source community".
Monocrops are more vulnerable to disease because the same (biological) exploit works on the entire population. In our Linux biosphere where there are dozens of major, varied configurations sharing parts but not all of their code (and hundreds or thousands of minor variations), a given exploit is likely to fail somewhere, and that failure is likely to create a bug that someone can notice.
It's not foolproof, but it helps keep the ecosystem healthy.
