Being a distinguished engineer at Mozilla doesn't necessarily make one far more qualified to understand the vast array of potential implications of Google gaining monopoly power in a variety of web sectors.
No, but it might. I'm sure the author has spent vastly more time looking at web standards and trends than I have and as such, his opinion should carry more weight than your average person.
You've simply pulled out a variation on the old "correlation does not imply causation" retort.
No, I pulled a more wordy version of "that's an appeal to authority fallacy". And I believe my point still stands. The author is speaking of issues that are several orders of magnitude of complexity above "writing amazing web software at Mozilla" and also impacted by a variety of fields that are very different than software engineering. Thus he is only marginally more informed than your average HN user.
It also gives him an ulterior motive. I am happy to hear what he has to say, but "just trust me" is not convincing.
To be clear, I am not accusing him of dishonesty, but I don't trust him to be impartial. People have a tendency to overvalue the thing they are working on.
You've simply pulled out a variation on the old "correlation does not imply causation" retort.