Again, I don't see what Secular Humanism has to do with anything at hand here.
Something that's very important to remember about atheism is that it isn't a religion or set of beliefs. The one thing that all atheists definitely have in common is their lack of belief in God/gods. You can be atheist and a Secular Humanist. One can be atheist and simultaneously be all sorts of other things, and have all sorts of beliefs that may or may not tie into one's atheism. But atheism is not interchangeable with those other aspects.
the author of the article makes the exact same mistakes as the writer(s?) he's decrying.
I do think that the author doesn't properly define atheism, but I don't see what mistake the author has made that the writer of the issue in question made.