If I had a blog, there’s an extremely narrow domain of knowledge I would be “allowed” to write about by this commenter’s standards.
This particular blog post is acceptable in my opinion because they aren’t making some crazy claims, it’s just a collection of simple observations and amusing conjecture.
People can challenge things casually or critically, and it's not meant to be taken personally -- and even if it was, easily ignorable. Good to have some organic haters (not saying the above commenter is, just saying generally among the public masses) to monetize the energy and attention.
The post doesn’t read like a textbook. It reads like someone’s casual musings.
There are other cases where I think authors overstate their position of authority, but the tone of this blog post doesn’t have that.