If you ask Tor exit node operators, they all share the same experience: Abuse is very low in comparison to the traffic they're pushing as a whole.
And yes, technology can be misused. So can a hammer. Tor protects everyone. Who is to judge about what is "bad" and what is "good"? US Government? Google?
There's an estimated number of at least 10,000 bridge users EVERY DAY. I don't think any criminal would go through the pain of using bridges, so that must be people behind firewalls in totalitarian countries.
Also, if you're up to something not good, it's always easy. As a criminal you can buy bot nets, pay servers with stolen credit cards, etc.
Wikileaks activists and whistleblowers rely on Tor. Assange has publicly stated that by running a Tor relay you can help the backbone infrastructure.
Wikileaks would not exist without Tor.