How in the heck can you plausibly correct someone else like that? You (almost certainly) don’t know that person, even in passing.

People can learn from watching a documentary just as well as they can learn from reading, but reading teaches you how to interpret language as you continue reading, and other forms of information delivery convey understanding of their own mediums in their own ways. I would not have learned how to quickly spot a terrible documentary over a great one if I had not watched so many in my life. It doesn’t mean I didn’t learn anything because I watched and listened instead of read, it just means that I didn’t read the documentaries.

Pro tip: don’t correct people about their own lives.