Relative to the general population baseline, adults can and do handle those topics. More so in real life. A community that prides itself on better thinking and debating practices should produce above-average-quality discussions on these topics, rather than flee from them like they bring about the death of the community.
If ordinary adults outside LW are generally content to discuss these things and some people on LW are not, this may indicate not that the LWers in question are intellectually deficient but merely that their standards are higher.
This is the kind of view that's highly prone to self-flattery and therefore rings my alarm bells. What I mean to say is not merely that they're content to do so. It's that they're confident that these are harmless, and that they can withstand whatever disagreement they have. People don't have strokes, marriages don't break and civil wars don't start just because people occasionally argue about the artistic merits of the most recent blockbuster. Most of the time in fact the effects are net positive -- people get to know each other better and have an excuse for interacting. That's what they signed up for in the first place.
what you meant was "Of the things LW actually discusses much, rationality is the only thing that I find interesting [but there are all kinds of other discussions I'd be interested in having here if other people were willing to have them]".
Indeed. Also, rationality is closer to the stated purpose of the community than the rest, and that was the reason for me bringing up the question in the first place.
should produce above-average-quality discussions on these topics, rather than flee from them
"Above-average" is really not a very high bar to clear, and any discussion about which nothing more positive could be said than "it's above average relative to the general population baseline" would be a sad thing indeed to see on LW.
That's the kind of view that's highly prone to self-flattery
No doubt. (Though, as it happens, I am perfectly happy to discuss many of the topics FrameBenignly listed, so suggesting that some people on LW might...
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.