Those were quoted a part of the initial public response to Arc, it didn't really go into why they were bad things - and the impact they had. The fact that they were part of blog chatter when Arc was released only is, to be blunt, really at best only marginally interesting. e.g. Have these things changed? Are they still relevant?
Being built on top the JVM gives you access to libraries - is this the meat? If so, I think most people already knew that. I think the "Ipso Facto therefore Clojure will be the 100 year language, not Arc" is a bit of a leap given all that.
I don't think the Author needs to justify anything - I don't need to agree with him - I'm just saying I got no real content out of this article.
You're right, probably taking it too seriously, but I'm of the view that even something lighthearted has to have some content (in fact, that's where humour is at it's peak).
"Adding powerful namespacing coupled with the fact that it’s built on top of the JVM dispels the questions and gripes aimed at Arc from the start."
That's the real meat. The rest is mostly anecdotes and humor, but it's cute writing.