In the context of the hypothetical physicists, it does not help them resolve their confusion to point to the hand shaking. Their mistake is in only counting the work done by the hand to the object. Once they've made that mistake, telling them that the hand shakes would not change their minds, since it doesn't show net work being done by the body in that respect, which is why I made the comment you quoted.
The mistake could only be corrected by pointing out the incorrect model of how humans generate lifting force.
So while your point is correct, and perhaps obvious, one should also remember that it doesn't address the specific mistake I criticized.
It seems to me that usually, when someone says "ethics" on lesswrong, ey usually means something along the lines of decision theory. When an average person says "ethics", ey is usually referring to a system of intuitions and social pressures designed to influence the behavior of members of a group. I think that a lot of the disagreement regarding ethics (i.e. consequentialism vs deontology) is rooted in a failure to properly distinguish between decision theory and what society pressures people to do. Most lesswrong users probably understand the distinction fairly clearly, but we only ever talk about decision theory. Why don't we talk about the social meaning of ethics?