Your claim that "pitfalls are not inherently aggressive", while true, is not backed up well. While you do provide a link, a summary and explanation of the evidence provided is advised when making a claim to support your main point. Reading through the link you provided, the American Society for the Prevention of Cruelty to Animals(ASPCA)--an organization dedicated to protecting animals from poor environments and circumstances--argues that pitbulls, as well as all dog breeds, are subject to a combination of nature and nurture. The practice specialized breeding throughout history for dogs to carry out specific functions has influenced the aggressive outlook on pitbulls due to them being bred to fight one another--but it does not determine their temperament entirely. In fact, genetics are much more complex than a simple gene for aggression, especially when mixed breeding comes into play. In addition, the environment and socialization of a dog is far more important than their genes alone.
While the source provided does seem reputable due to the fact that it is an official animal care organization, reading through the article, I could find no links to outside resources or information for their argument. Thus, I investigated myself, and was able to find this study from Universities Federation for Animal Welfare on how there is no evidence to show that pitbulls have higher rates of aggression than other dog breeds. The study compared the analyzed behavior of 40 pitbulls and 42 other similar sized dog breeds from a shelter. When looking at it, very few dogs were returned for aggressive behavior, but in comparison, pitbulls were actually returned less. I do not think that this source is perfect; I think that its sample size could be bigger and more trials would need to be run. However, for the purposes of this claim, it is useful support and has valuable data to support the fact that pitbulls are not inherently more aggressive than other dog breeds; indeed, a lot of their perceived aggression seems to lie in stigma and expectation rather than reality.
Here is the link to the study:
https://faunalytics.org/wp-content/uploads/2015/05/MacNeil-Allcock%20Pitbull%20Study%202011%20UFAW.pdf