That's one of the reasons why you try to mitigate bad side effects: so that people who'll suffer on net from the efffects will STFU.

In theory, yes. And I'd much prefer a one-time ("extortion") payment to a domestic industry to allow cheaper imports, than allow the global economy to remain in a perpetual rut just so a few people don't have to change jobs.

But the fact that this alternative is Pareto-efficient doesn't mean the potential sufferers will STFU -- rather, it costs the alternative its public support, probably because the average person, sympathetic to the domestic industry, still sees it as extortion. And the people in the domestic industry don't want to see themselves as extortioners either! (Relevant Landsburg post.)