Bloomberg saying "you can't teach a coal miner to code" is worse than offensive. It's akin to saying "you can't teach a slave to read." He should be called to account for it.
While his larger point about needing a variety of solutions to unemployment problems is fair, coding is a skill exactly like reading and writing any natural language. No one would hold up Hemingway or Tolstoy as a reason not to teach reading and writing, so please don't do it for technical skill. You don’t have to land a job as a senior engineer at Google or Facebook to develop coding proficiency and benefit from that knowledge. We live in a technological society now; people should be encouraged to adapt, not discouraged.