I also made this mistake (although, to be fair, on the issue of torture, Obama genuinely was an improvement.)
How do you now? The Obama administration continues to ban photographing equipment which was one of the policies to suppress evidence of US torture.
Torture got outlawed in the late Bush administration. People responsible for the torture project had no problem raising in influence within the Obama administration. The Obama administration continues to run black sites.
What is something you used to believe, preferably something concrete with direct or implied predictions, that you now know was dead wrong. Was your belief rational given what you knew and could know back then, or was it irrational, and why?
Edit: I feel like some of these are getting a bit glib and political. Please try to explain what false assumptions or biases were underlying your beliefs - be introspective - this is LW after all.