Pitbulls or if you mean actual American Pitbull Terriers, as well as American Staffordshire Terriers, are not supposed to be human aggressive. They have high prey drive, which leads to dog aggression (which does not make them bad it just means that you have to be aware they don't mix well with other dogs). But they should never have any human aggression genetically. In fact they were bred that way so that humans could take them out of the fighting ring without getting hurt. But most of what you see in rescues, etc., are not well bred pitbulls and are typically mixes that should not have been mixed, leading to these issues. Combine that with not being raised by people who understand these dogs: I would not recommend an APBT or staffie to a first time dog owner - and I've owned 2 mixes of these breeds.

But as to your analogy with labs, a lot of this is genetic dumpster fire stuff - meaning they've been bred poorly or mixed with other breeds and their poor genetics are all haywire. My rescue Algo Más is that way. He's reactive, and it's genetic, and we are able to do a lot to counter condition it and manage it, but to an extent it's how he's built.