I think that you are taking a very narrow view of Corbet's intent with the article.
You seem to imply that Corbet is arguing against CentOS's legitimate right or potential to continue to exist. My reading is that he is simply commenting on the validity of Red Hat's business model of offering payed support. And backing it up with real numbers. Timely updates is quite important for many security-sensitive businesses.
"If you need serious support, you should pay for serious support" is an entirely valid statement. You seem to have skipped over the word "serious". It's right there, twice! :) Cost-conscious companies out there that are yet paying for RHEL support obviously have different needs from that of most CentOS users.
Your presupposition seems to be that free software is more than pro-freedom; that it is necessarily anti-commercial. I am confident that even RMS will disagree with you on this.