With my previous (incorrect) knowledge, attempting to influence someone's sexuality had no redeeming features. Its only effect was to create confusion, self loathing and other negative effects/emotions in adolescents. If, however it can be effected by the environment then there exist situations, possibly controllable situations where children can be systematically influenced to one sexuality or other.
My immediate reaction is that people should still be able to figure it out for themselves, but the situation is less black and white than before. If for example gays turn out to be significantly happier and more productive throughout their life than straight people, does it then become moral to attempt to influence potential homosexuals to increase their changes of becoming gay? The opposite argument also exists if you replace gay with straight in the previous sentence. It is no longer an open and shut case, there exist worlds where the optimal thing to do is morally repugnant to me. It pits my value for autonomy against my value of optimality.
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.