Once you've decided you're righteous, you lose the ability to tell political positions from moral. You think whatever is "best" for the body politic is morally correct. You forget that these prescriptions come not only from your political opinions about what are the correct goals, but also your completely unjustified straight-up-guesses about the correct steps to *achieve* those goals, which causes will lead to which effects, and how the rest of us will behave in response.