That's not necessarily true. As the percentage of nonsense goes down there is a critical region where people will start to trust it implicitly without further verification. This can - and likely will - lead to serious problems which will occur downstream from where these unverified errors have been injected into the set of 'facts' that underpin decisions. As long as the percentage of nonsense is high enough an effort will be made to ensure that what comes out of the system as a whole is accurate. But once the percentage drops below a certain threshold the verification step will be seen as useless and will likely be optimized away. If the decision is a critical one then it may have serious consequences.

You see something similar with self driving vehicles, and for much the same reasons.