It is very much a valid argument. SpaceX has been working on this issue for years.

https://theconversation.com/a-million-new-spacex-satellites-...

FTA: "SpaceX has done a lot of engineering work to make its Starlink satellites fainter. They are still too bright for research astronomy, but thanks to new coatings, their brightness has not increased dramatically even as SpaceX has launched larger and larger satellites."

Of course it’s a serious argument. Anyone using telescopes or doing Astro photography now sees Starlink satellites leaving trails all over the place. And that’s with a small number compared to the 1 million satellites they are proposing. It’s a public resource that a private company is stealing from all of us.