With competition it is a red queen's race unfortunately. It is natural in an emergent sense even though the circumstances are synthetic. If they don't someone else will and even if they held existing jobs sancrosanct they will be displaced by a new party who doesn't have existing jobs to protect.
We don't get to choose whether we're in the race or not, but we do get to choose how we run it. I get the "these are forces at work, not humans" argument, but I think it underestimates the solution space available to the humans in the scenario (to be fair, they probably do too).
Nature is pretty damn cruel and selfish at times. Just because it utterly sucks doesn't mean it isn't natural - similarly healthy has the question of healthy for who and when?
Illness in herd animals is healthy for wolves by making them easier to kill without injury.
The industrial revolution saw major growing pains and destitution but raised standards of living greatly.
Your somewhat patronizing analogy misses the point. If our ultimate goal as a species is to survive and live well, then cutting hundreds of thousands (millions, actually, if you think about the implications of automation in other areas) is in conflict with that goal, thus 'unnatural'.
If the goal is to live well, that has nothing to do with doing jobs that a machine can do. Automation is not in conflict with the goal of people living well. If anything, it's the best tool we have to achieve the goal.
The conflict with the goal of people living well is that we don't want to take wealth from those that have it and give it to those that don't, without making the ones that don't have wealth "earn it".
Otherwise, there is nothing stopping societies from gathering up all the extra profits from automation, and using it to invest in education, healthcare, reducing number of work hours, increasing vacation time, i.e. living well. But we would rather not have that.
The purpose of work is to do something useful as well. Makework is even more unnatural which is what automatable jobs being kept for the sake of employment only are. That level of waste mounting isn't good for living well as it calls for what is essentially wasted resources and lifetimes.
The true issue is adaptability or lack of it in an economy. The replaced should be doing something actually useful but that process is less than straightforward.