What makes you think diversity helps in any environment? I think that homogeneity is a great help for efficiency, which is often important. Diversity has its uses, but it's not for everything.
I was referring to the overall environment, not any and every combination of 2+ people.
A homogeneous group certainly can be the best team for a given task. I'm only suggesting you have a sub-optimal environment if the only teams you can put together are homogeneous ones.
That said, the self-perpetuating 'Boys Club' stereotype is a problem I care about.
In short: It causes nothing but trouble. It drives away more than just women. It creates stigma and bias and I don't see any positive return from it.