Even if we assume 99% of Tor is CP, that doesn't mean blocking Tor will remove 99% of CP. In fact, it probably will have no impact, as criminals will just use other methods, as they are well funded unlike oppressed journalists.
Surely there are also other ways for whistleblowers/journalists to communicate secrets. And why do you assume the random child porn creator/enjoyer is well funded? This kind of crime is more about availability and lack of consequences than money. Tor makes it invisible as no one will ever admit to it, but it's still easily available to anyone, with no consequences. Why are you so convinced that going after it is necessarily useless, necessarily harmful and necessarily wrong? I can't help but feel that it's a principled position, and that no amount of harm done would justify making it law-enforceable to you. How much lawlessness should we accept in exchange for how much whistleblowing? Any amount vs the slightest act doesn't sound like a good balance to me.
