My Responses: (1) You had a problem with Mibbit users that you seem to have solved. Why do you need to argue so passionately against Mibbit if it was so easy for you to solve? Did it take you hours and hours to figure out how to ban Mibbit users from your channels? There is a post by someone from #perl that says they even figured out how to extract the original user's IP and that they were able to get rid of most of the bad users by banning the default Mibbit prefix. That doesn't seem too hard to me (banning the nick prefix). Could you enlighten us as to why Mibbit made it a PITA to ban all Mibbit users from your channel?
(2) I don't see any claims that Freenode knows that Mibbit is misreporting its users' IP addresses. Whether or not they have incentive to do so is irrelevant because it does not even seem to be a stated reason behind Freenode's decision. Therefore presumably Freenode either believes what Mibbit reports or they don't think that it's a minor issue. In either case, I don't see how it should be a large part of this discussion. To further argue against your point, Freenode supports Tor. Tor's stated objective is to help users be anonymous. Should Freenode also ban all users from ISPs that allow them to reset their modems to get another dynamic IP address?
(3) I see lots of disagreement with Freenode's decision, and calls for reversal but I have yet to see someone claiming that Freenode should be required to never ban a certain client. Just because someone disagrees with a decision doesn't mean they believe that the person/group doesn't have a right to make a decision. Much in the same way that just because Freenode has the right to make this decision I am not required to like it.