They only created a tool. Tools can be used for many purposes. I can smash someone in the skull with a hammer or I can use it for construction. Similarly, should the Tor, PGP, Bitcoin, etc authors consider that their tools could be used for malice and stop because of it? Tools are tools, they are simply implementations of what is possible with technology. Tools are inherently grey, not some simple black and white. It's about what you do with them.