This is a very good article, but I think some parts contradict themselves. Namely:

These preconceived biases arise because programming languages are as much social constructs as they are technical ones. A programming language, like a spoken language, is defined not just by syntax and semantics, but also by the people who use it and what they have written. Research shows that the community and libraries, rather than the technical features, are most important in determining the languages people choose. Scientists, for instance, use Python for the good libraries for scientific computing.

And:

Especially given that it takes only a few months for a professional software engineer to learn most mainstream languages, we encourage employers to make hiring decisions based on better metrics than the languages that a candidate knows.

I need to check the actual research, but I doubt “only a few months to learn most mainstream languages” include time to learn libraries, which are, as claimed, more important than the technical features.

Another practical concern is that it is harder to interview people if interviewers and interviewees use different languages. If an employer of programmers whose primary language is Python prefers candidates who know Python, one reason is because it is easier to evaluate them. Candidates who don’t know Python may have better merits, but it will be harder to discern them.