I don’t think he’s calling them stupid, which both humans and animals definitely can be, I think he means an understanding of right and wrong, which also can relate to humans…
"The Staffordshire Bull Terrier’s reputation is built on hearsay rather than fact. On the way it looks, rather than the way it acts. It is often identified incorrectly. In reality, many of the dogs that show aggression are bull breed crosses. The purebred Staffie is a whole different ball game...