This point could perhaps be driven home by noting that the scientific method is, at heart, about asking questions about observations. For example, "Why do two objects of the same mass fall at the same rate?"

That's a fairly simple question that prompted Isaac Newton to formulate his theory of gravity.

Of course, questions in science are usually much more complex than that these days, especially in the "softer" social sciences. The power of diversity is the power to ask more questions, and more different questions. Without diversity, we're less likely to ask questions that advance human knowledge outside areas that are mainstream or conventional.

Science thrives best when questions are most varied, which strongly implies a need for diversity among researchers.