I dare say there are many things, in hindsight, that could have led to a more productive discussion. As it happens I'm not convinced you're right in this particular case, but I think arguing the point would be one level of meta too many.
However, it is simply not true that I called Dahlen reprehensible for bringing up the topic of autism. Less importantly, because what I called reprehensible was one of Dahlen's actions, not Dahlen the person. More importantly, because (as I have already said in response to your making the same false accusation elsewhere in this thread) it was not simply "bringing the topic of autism up" that I found reprehensible.
(If whoever downvoted the grandparent of this comment did so because of deficiencies in it rather than because they've taken a dislike to me, I'd be glad to learn what deficiencies they found. It looks OK to me on careful rereading.)
For example, what would be inappropriately off topic to post to LessWrong discussion about?
I couldn't find an answer in the FAQ. (Perhaps it'd be worth adding one.) The closest I could find was this:
However "rationality" can be interpreted broadly enough that rational discussion of anything would count, and my experience reading LW is compatible with this interpretation being applied by posters. Indeed my experience seems to suggest that practically everything is on topic; political discussion of certain sorts is frowned upon, but not due to being off topic. People often post about things far removed from the topics of interest. And some of these topics are very broad: it seems that a lot of material about self-improvement is acceptable, for instance.