What worries me is the apparent refusal to engage with the rational critics of reductionism. But I am mainly thinking of critics in fields other than physics - politics "there is no such thing as society", Skinner's psychology, "there are no thoughts, only stimuli and responses", not to mention developmental biology, weather forecasting & even mechanical engineering analysis, none of which actually get near "the territory" of quarks and leptons. So I am beginning to suspect that reductionism is used in a special sense by EY, more or less as a synonym for monism. And it's true, I wouldn't want to defend "substance dualists".

What you are calling reductionism here is the refusal to countenance some higher-level properties. But, in fact, most reductionists do countenance most h-l properties. What makes them reductionists (which of course is not brought out by the broken LW wiki definition) is that they think all the h-l properties they countenance can be explained at a lower level. BTW, people who don't countenance any h-l properties, states, or entities are called mereological nihiists, not reductionists.