I believe it's "no machine in the image of a human mind" and that is generally regarded as like space-amish; If a person can do it a person must do it, and if a person can't do it we'll do magic space eugenics for thousands of years until we build a person that can do it.

In the OG books it was implied that the Butlerian Jihad was ideological rather than practical. The people of that era thought that reliance on thinking machines was somehow damaging to their humanness or something and so they destroyed them all. The ret-con ass pull of having evil robots was purely the Son's thing.