You are essentially making the luddite case. The counterargument usually goes like this: yes, people would be fired and there will be serious pain in the short run; however the machines will drastically improve productivity, therefore reduce prices, so real wages will go up along with demand and the extra income not spent on, say, buying feed stock for your horse, will go in creating other jobs and economic sectors that will make use of the available labor. The government can and should ease the transition by offering skill-training and incentives.

While economically sound, I'm skeptical this process can go on forever. The human biology and mind is clearly limited, while the progress of machines does not seem to be. So eventually you will hit a fundamental limit where larger and larger chunks of the workforce will simply be too old, uneducated or simply too human to keep up.

How close we are to this fundamental limit it's anyone's guess, but I would venture to say we are closer than most think. At the point where a serious part of the population is unable to participate in the labor market, this ceases to be an appropriate system to distribute the fruits of economic activity and some form of basic income is required to maintain social order.