This report gives the opinions of expert behaviourists and consultants on the reasons why some dogs may be aggressive towards people. Of the 215 experts who responded, some 74% argued that breed was either not at all important or only slightly important, whilst an overwhelming 86% believed it was due to the way that the dog was brought up by its owner.

committees.parliament.uk/writtenevidence/…/html/

The law on dangerous dogs refers to specific breeds of dog as ‘dangerous’. However, we believe that breed-specific legislation ignores the most important factors that contribute to biting incidents – primarily anti-social behaviour by irresponsible dog owners who train their dogs to be aggressive or do not train their dogs adequately.

…org.uk/…/dangerous-dogs-deed-not-breed/

theguardian.com/…/banning-some-dog-breeds-in-the-… - study in comments

There is a ton of research on the issue.