It seems there is not an economic fallacy so basic that it will not be espoused at some elite university.
Before any MIT econ dons start invading the labs of their funding-rivals in the engineering department to smash any robots or mechanized looms they find, I hope they will take a second to read this passage from Mises:
The confusion starts with the misinterpretation of the statement that machinery is “substituted” for labor. What happens is that labor is rendered more efficient by the aid of machinery. The same input of labor leads to a greater quantity or a better quality of products. The employment of machinery itself does not directly result in a reduction of the number of hands employed in the production of article A concerned. What brings about this secondary effect is the fact that–other things being equal–an increase in the available supply of A lowers the marginal utility of a unit of A as against that of the units of other articles and that therefore labor is withdrawn from the production of A and employed in the turning out of other articles. The technological improvement in the production of A makes it possible to realize certain projects which could not be executed before because the workers required were employed for the production of A for which consumers’ demand was more urgent. The reduction of the number of workers in the A industry is caused by the increased demand of these other branches to which the opportunity to expand is offered. Incidentally, this insight explodes all talk about “technological unemployment.”
Tools and machinery are primarily not labor-saving devices, but means to increase output per unit of input. They appear as labor-saving devices if looked upon exclusively from the point of view of the individual branch of business concerned. Seen from the point of view of the consumers and the whole of society, they appear as instruments that raise the productivity of human effort. They increase supply and make it possible to consume more material goods and to enjoy more leisure. Which goods will be consumed in greater quantity and to what extent people will prefer to enjoy more leisure depends on people’s value judgments.