Why do you care? There's no reason to rant. If you want to do your duty to protect people and yourself from this problem just go out and vote. Vote for someone whose against these breeds and wants to get them banned in your community. Better yet run for office. Or organize an informational community meeting regarding the issue, get a petition signed, and turn it in to your mayor for review.
Otherwise, stop ranting. Anyone would have been happy to give you more information, or answer your questions reasonably had it not been so bias or accusatory. "lack of common sense" what is not sensible is someone discussing, or even fully forming an opinion, about a subject they admit they do not fully comprehend. So I wouldn't be talking about neutralizing opinions. Why don't people do their research before forming opinions?
"so prevalent at the bottom end of society" - do you realize how ridiculous this statement alone sounds? Grow up. When somebody asks a question, in the way that you have here, it often winds up being the very reason people don't even want to listen to this argument. You're not doing anyone any favors by trying to present information, argue, or even raise an opinion in this fashion.
You're correct. You are not an expert. If you were, or if you did some more research (*and to answer your question, "And why oh why are all such animals not banned completely?") you would quickly understand most of the research is still under heavy debate, which is why they aren't currently banned completely. You have to have irrefutable proof, and even then somebody from your community or gov. has to really want to get it done. Depending on where you live it could take YEARS if not months and that is if someone is determined. Based on community size alone (in your city, town, village, wherever) there aren't enough dog attacks, or issues with these breeds that put a serious strain on public safety. Even if worldwide or even nationwide there are many cases if there's only a small number in your community no one will really care unless there are quite a few gruesome incidents, usually from repeat offenders, and a large group of supporters requesting change. People would just as soon eradicate the only animal responsible for the attack, than ban a breed, or even completely eradicate a breed through genocide or sexually altering them (depending on your country). To most, banning a breed is a radical notion. Great Britain is one of the few countries to have banned pit bulls, but some still fall through the cracks. You have your work cut out for ya.
Best of luck.