I know who Elon Musk is and his contributions. My apologies, but I have never heard of the author and their contribution, and why should I fucking care what they (and 80 of their politically like-minded friends) think out of a thousand other members? Obviously the Royal Society's own relevance is hinged on picking who they should keep between two opposing members.
Fame isn't relevant. I've not heard of all bar one of Trump's new and previous cabinets combined, and the one I have heard of, I only know about due to the brain worms. Zero of Biden's, zero of Obama's. Possibly two of GWB's? I've only heard of two of the people who work at SpaceX, and that's Musk and Shotwell none of the rest; likewise none of those under Musk at X, TBC, Neuralink, Tesla, Starlink, Solar City. Someo…
Of course it is relevant. As your post admits the author's recognized in some community that led them to post such things. If it weren't for their relative fame, their letter would be ignored. My take is about the relative fame of them vs Musk. Both are members of Royal Society, so that credential is moot. What else does the author have to make their case? Why should one listen to them, and take their opinion seriously, over Musk, who is the first and only one in the world who has caught rocket boosters in the history of the world? What is the author's accomplishments?