Who is only looking at one correlation? We all take into account the information we have. More information is better. If they had provided more information, it would have improved each reader's overall picture.
>Or would it be better to only discriminate against dogs and not their owners? We all know how much the dogs use USPS.
I don't know what this means.
>why not take it on by promoting better dog upbringing?
I do promote that. I don't know where you're getting this from.
Back to the idea of harm avoidance:
Let's say we discover that the only factors that determine bite risk are how the dog is raised and how you behave around it. And let's say there is a non-causative correlation showing breed X has a high bite risk. Then it would be reasonable when adopting a puppy to not consider breed X a high bite risk, but it would also be reasonable to consider breed X a high bite risk when encountering one you didn't raise yourself, and therefore e.g. not allow your child to interact with it (or whatever precaution makes one feel comfortable). More information is better.