Agreed - OP's criticism is way over the top.

This blog post is very much "first principles" for the layperson. It's not the level of "first principles" that a trained physicist would expect (where there would be rigorous derivations involving dielectric functions and the like), but it's great for a layperson who wants to understand why the world looks the way it does.

So then, why use that phrase and not a more accurate one?