We shouldn't right wrongs by deliberately capping economic efficiency, especially in sectors that are foundational to the rest of the economy (e.g. maritime trade and energy).
We shouldn't. Dockworkers should allow automation, and those jobs that remain should capture a fair share of the increased productivity in increased wages.
The difficulty is that owners don't just voluntarily hand out "fair shares" to workers who agree to play nice. The only reason workers get paid at all is because if they stopped getting paid, they would stop working.
Once enough automation is introduced, the owners really have no incentive to pay a fair share to anybody whose labor they no longer need. So any promises to "share the wealth" that comes from automation ring hollow.
Once business adds additional automation, (a) the business made additional investment in the automation, (b) the remaining jobs tend to be higher-skill, (c) (after recouping cost of automation) the business now has better margins and can afford to pay the remaining employees more, (d) because of (b) and (c), they usually do pay their remaining employees more as a way to retain now even more critical labor.
Businesses rarely automate the hardest / highest-skill parts of the job first. Why would they? There are lower-hanging fruit.