Transgender people are fundamentally delusional.
This was mostly typical mind fallacy, supported by an argument that rested on an availability heuristic problem, which was this: I'm aware of no record of trans people historically, so the phenomenon was not present; therefore, the prior on being born into a male/female body is overwhelmingly that you are a man/woman (respectively), and you need an enormous amount of evidence to overcome the prior. (This isn't how I would have formulated it at the time; I wasn't familiar with Bayesian terminology and had only intermittently read the sequences, and that in small, scattered chunks.)
Hmm, "delusional" is a bit underspecified.
How about "There's no solid evidence for a gender bit in the brain. While many or most transgender people feel something, explaining that feeling as "I'm an X brain trapped in a non-X body" is essentially a memetic phenomenon. Additionally, genderqueer and non-binary persons are typically participants in a memetic fad."
I think that's what I believe; summarizing this as "trans people are delusional" seems harsh and uncharitable to me, but I can see how someone might say that's exactly what it is. If you think now that the above is obviously wrong, I'm very interested in arguments/evidence.
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.