The author should write whatever he pleases. But I believe it would be proper to use a language directed to a broader audience when writing a public blog post. I also believe that the author was trying to be funny and had no bad intents what so ever, but either way these tiny things matter if we ever want to see diversity in our field.
I would also like to add that your argumentation is quite unpleasant to me. I read it as you believe that diversity is this annoying thing that destroys the good ol' "all dude internet". Would you care to clarify what you meant?