Diversity at work

I know everyone comes from very diverse background, culturally, economically and academically. My HR project was on diversity and the benefits of embracing it in wide open arms. Maybe I was too engrossed in promoting diversity at workplace, I myself totally believed in it. The joy of working in an environment where diversity thrives is something that I once looked forward to. With different inputs, ideas and perspectives, complimenting each other, great things are just waiting to be achieved. One small flaw in this hypothetical situation is the assumption that everyone one will contribute constructively. There just seem to be a special breed of people who just know how to make non constructive protests to stop work from being done, including endless excuses to not work, creating unnecessarily delays and making life difficult for everyone, in short kpkb. Sometimes I really wish these people will just shut up instead of opening their mouth. If I have the chance, I would make some minor amendments on my HR project and emphasize more on the word "constructive". This led me to another question, how did kpkb-ers get recruited in the first place.