I don't see that he wants it shut down - all he wants is to be made sure that people are aware of the risk. If your alternatives are to communicate in plaintext-equivalent (that is, broken crypto) while thinking you are protected or to communicate in plaintext, knowing that eavesdropping is possible, the latter is the better alternative! And there are even more alternatives already, like meeting people in person, or using PGP, or any number of things. Even using cryptocat while knowing that it is not reliable is better. There are tons of options right now, and the worst of them is to use an unreliable protection while thinking it is protecting you, hence the criticism.