certainly I think the ethics is important. Mostly because highly homogenous groups tend not to be inviting for outsiders to the group. It may be intentionally done, but undetected due to lack of diversity, but even harder to discover is implicit biases that form stronger in homogenous groups. So even if you're not actively pushing out minorities, you may be passively doing so which is IMHO unethical when knowingly allowed to fester.

But from a business perspective, this means you're dramatically reducing your hiring pool, even if unintentionally done. So you may be missing out on a lot of people who may improve your product.

Now of course hypothetical value is hard to quantify, but you can quantify how many people you're potentially excluding. A good way to do this is see how many percentage points your makeup is versus college graduates, especially local. It doesn't need to be a match but it also shouldn't be dramatically off.

Then repeat through each tier of your company. A lot of companies struggle with turnover even if their hiring is adequately diverse. This is potentially due to years of forming homogenous in crowds that promote within themselves.

Therefore diversity can help identify procedural issues in your company that could result in better hiring and promotion practices, even if it doesn't lead to diversity itself.

The best thing to do here is collect data. A good analogy may be that you shouldn't test your software with low variance data sets. So why would you test your company with low variance data sets? It would highlight bugs in the system that is your company