This article glosses over the historical mistreatment of dogs where millions were killed yearly, and then cherry picks and details a bunch of examples of Bad Things happening to dogs nowadays. It ignores all the benefits of neutering just to make a point. Also, my dog is neutered, and is not aggressive at all, EXCEPT towards un-neutered dogs. Where I live it's illegal to bring an un-neutered dog to the dog park, but…
Could this be a nature vs. nurture case? I don’t have much experience with dogs, but is it possible that the people who don’t neuter their dogs raise them differently? In my social circle at least, neutering your dog is the social norm. If you don’t, and then break the law to take your dog to the park, most people would say you’re acting irresponsibly. Perhaps these sort of people aren’t compelled to train their dogs…
That said, there could be some correlation there where less informed owners who don't train their dogs and don't neuter them. In general though, neutering has been shown (in the same dog) to help curb some unwanted behaviors. Trainers can and will recommend neutering in some cases [0]
[0] For example, Victoria Stillwell is a well-known trainer who recommended neutering this dog: https://www.youtube.com/watch?v=rXaGxFzv-GM