"...or the worst source of injustice"
Or both? Like most of modern society's advancements? We have both air conditioning and laser-guided missiles. We have the most food in history and a lot of starving people worldwide. The car both unlocks people's ability to do more, and poisons them/the environment. It's not either/or, it's tradeoffs.
"As the models become more powerful, they could begin to act against our interests and we could lose control"
This will never happen, and the proof is Bill's own words. He is already acting to keep control. Humans don't just sit back and let themselves get steamrolled, they act to put things in place that protects them and retains their own power and control. The machines will never pull a fast one on us because we're already too paranoid and power-crazy.
"In his essay, Gates proposed taxing AI or robots the way you would pay a human employee's payroll tax in order to slow the shift away from using human labor."
This is like putting a tax on the Cotton Gin. What would be the point? To artificially raise the price of goods and services? The whole point of technology is to ELIMINATE HUMAN LABOR. It's the reason we have computers to begin with.