I was going to run an exit node when I first learned about Tor, but realized that the cool positive use cases I was imagining it would help with could be effectively done in other ways. In some cases those other ways might not be as easy, but there would be enough resources available to the people involved to get the job done.

It seemed likely that it would be the horrible use cases it would benefit the most.

Balancing an increase in the efficiency of doing good things that could already by done other ways against greatly benefiting horrible use cases made it so that I could not morally justify it.