Why not just unblock port 6667 for outgoing connections? Since existing mechanisms (see http://it.jhu.edu/restricted/infosec/blocklist.html ) automatically detect and block hosts with malware which uses IRC, clearly, blocking outgoing traffic on port 6667 only blocks legitimate traffic because hosts sending traffic from malware are already automatically blocked by the mechanism seen at http://it.jhu.edu/restricted/infosec/blocklist.html .
I would be have to discuss this issue further.
Thank you.