Viva la programmacion!..
We humans are very good at both forming groups as well as self-segregation. There will never be total conformance and homogeneity. If you think certain group of people fall into that category, that's because your own lack of understanding of them rather than them being the same.
In fact, if we all spoke the same language, there will actually be more understanding and less perceived sameness or difference.
People don't live to achieve total understanding and zero perceived difference with everyone else, rather, understanding and sameness exists to facilitate living.
Slowly getting to know people who spoke no common language with you and finally both of you managing to build rapport and communicate clearly with each other is a fulfilling experience. Advocating monoculture of language isn't too different to advocating a monoculture of crops, destroying diversity of life in the name of efficiency.
Efficiency facilitates living. Sacrificing experience of life in the name of efficiency kind of defeats the point.
You want more, more of what, exactly?
Like you said, the idea of everyone speaking the same language could never result in total homogeneity. However, you could lose out on some of the deeper insights and developments without language to filter out the noise. I believe that it would be a huge step backwards, but obviously you may disagree.