True, but I think there is a distinction to be made between designing a protocol like tor and actually providing the service of setting up tor sites for people who you suspect are using them to distribute child porn.
It's not about whether it could be created for smothering people. If you're a tailor, and someone says to you, "I need a special kind of jacket with a loop like this that I can use to strangle people with,"* and you make that for them, then yes, you are liable when they indeed use it for that purpose! As for who decides whether the creator knew it would be used for an illegal purpose, that would be the jury.
If before there was an internet, a terrorist group approached a technologist and described a network that they required to better organize terror plots, then YES, that person should be held accountable for the uses the group puts it to, even if it eventually has positive consequences as well.
On the other hand, if a person makes and distributes anything, dangerous or not, with a legitimate use case in mind, they should absolutely be held blameless if it is then used by someone else to commit a crime.
*Assuming of course that a "reasonable person" would actually believe the person was indeed going to do that, since it comes across as pretty bizarre...