What are 3.5 million people going to do if they're suddenly out of a job and have to change career completely?
I am far from being a Trump supporter, but it would be easy for authoritarian politicians to ride to the White House on the grievances of millions of voters who had their livelihoods taken away from them by automation. Trump's promises to bring back manufacturing jobs were fueled by the automation and outsourcing that have already eliminated millions of positions. So Trump's victory in 2016 was already due in part to a backlash against automation.
No society where an average person - of average intelligence, average skills, average potential - cannot make a good living for themselves, can survive as a civilized society.
We can't all be developers, engineers, or doctors.