This is a very nice and thorough refutation of panpsychism, but I suggest that your brush is slightly too broad. The problem is your use of “proto”. I’m a physicalist for all the reasons you provide, but I’m also a panprotopsychist. Every physical thing has a property that is one step away from being involved in experience. That property is mutual information, following from the fact that every physical process follows patterns we call physical laws. The proto-experience becomes experience when that property is used for a purpose. The best phrase I have for indicating an experience is pattern recognition.

So I balk when you say no one seriously thinks bacteria are conscious. No one seriously thought that water was made from hydrogen and oxygen, until they did. A single molecule of water has no resemblance to liquid, snowflakes, or humidity, just as the consciousness of bacteria has no (well, little) resemblance to human consciousness. But when you understand that the basis of consciousness is pattern recognition, you can understand how nature would produce a cell whose whole purpose is to be a general-purpose pattern recognizer: the neuron. You can understand how nature would produce combinations and hierarchies of pattern recognitions. You can understand how pattern recognition explains information integration, “global broadcast” , predictive processing, etc.

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[ok, I feel better now]