I Disagree on more than one level.

(a) There’s no (scientific) indication that he’s made a mistake. It remains to be seen.

(b) Admitting mistakes is one of the fundamentals of science. While humans are surely not eager to be wrong, no scientist can assume he’s always right or can’t be proven wrong (that would require religion on the scientists part).

I doubt Minsky would be making such a statement if he didn’t believe it on a scientific basis.