A town not too far from my summer home used to build ships. Big ships, exported to countries all over the world. Then in the 70-ies customers realized that welding could be done much much cheaper elsewhere and that the hull could cost significantly less. The shipbuilders then had a choice, keep doing the "advanced" part, which was the bridge and those parts, or keep trying to produce the whole ship.
They chose not to change their product, and now there are no shipbuilding going on there any more.
That city is now far from its former glory, although not as bad as Detroit appears to be. Can you see any way that the politicians in that city could have avoided the scenario they're in

Had the shipbuilding industry instead fired 70% of their workforce they might still have been in business, but the city would still be pretty much screwed since when a large employer downsizes to that degree there will be cascading effects where suppliers also will have to do lay-offs, which will impact shops, theatres etc.
The city would still be in almost the same sorry state that it's in today.

Rising unemployment correlates with a rise in crimes, and children who don't see any future for themselves tend to do bad in school.
Also, the guy is blaming unions for the state that Detroit is in.  Does he realize that salaries in the US can never drop to the level to be competitive with the salaries in many/most asian countries? The cost of living is too high in the US.

The guy did a bad analysis based on his agenda. There might be a nugget of truth buried in the garbage he's spewing, but given how he mishandles all other data, nobody will give it any credibility. Except those who share his agenda naturally.