I don't think they necessarily do - they're just saying what they think, but then other people read it and get annoyed (justifiably.)
That's the thing with blogs, the entire world can hear your opinion, and sometimes it would have been better if they didn't.
Actually in this article, when I re-read it, I think it is written in a sort of ironic/fun tone.
Although I love clojure, I understand the disappointment in not being "lisp all the way down" - there is something satisfying about the purity of that approach, if it is practical. Maybe one day...
I'm kidding.
I think it's a great language. As much as I value purity from an academic standpoint, I also need to eat. I'd rather see a 90%-pure Lisp that I can get a job in than a 100%-pure Lisp that I can't.
Moreover, I think Clojure will get more Lispy, rather than less, over time. In 2015, I think far fewer people will be programming in Java full-time, and the JVM will be optimized as a VM to support higher-level languages rather than to support Java as a primary language.