Oh no, he did indeed, but not there (at least all I can see is the commentary, but not the quote in Greek). He said that, but maybe somewhere else, the commentry is refering to this quote, though.
Unless this is the quote:
For you surely do not suppose that experts in these matters are reasoners and dialecticians.
[face=spionic]ou) ga/r pou dokou=si/ ge/ soi oi( tau=ta deinoi\ dialektikoi\ ei)=nai.[/face]
If that's the quote, then the translation you have is a very loose one indeed.