As if there were no correlation between that and the use of the service for distributing CP. I'm sorry, but I find it hard to get exercised about the invasion of privacy aspect, considering much greater invasions of both person and privacy that take place in the manufacture of child pornography. Liberty does not subsist in the oppression of others.
As regards Tor, it's extremely debatable that its existence has any impact at all on the distribution of child pornography. If you don't care about hurting people, there are way more effective ways to protect your anonymity than Tor.
In addition, Tor is an incredibly useful tool for fighting corruption in countries where online privacy would otherwise be non-existent.
So on the one hand it's a tool that gives anonymity to a group that already has it. On the other hand, it's a tool that aids in reducing human rights abuses across the board, including human trafficking.
Do you have more information or references on this? It seems very intuitively correct to me, but I was hoping someone much more intelligent than me has actually formalized somehow.
A system that protects the privacy of users who have "American" free speech is simultaneously a system that protects "criminals" who violate blasphemy, royal-insult, obscenity, or any number of other laws in other countries.