Like do they actually, reliably effect change in the way the activists intend?
Have they worked against Israel? Did they work against Apartheid South Africa? Could they work against Trump’s America?
My hunch is that they don’t, really, but can be a useful promotional tool for other issues. Like don’t buy American is a simple message. If people will listen to that, they may listen to reasons why, which maybe could build a movement.
But on the whole I am very sceptical, and would be interested in any reasons for or against boycotts.
For me it sorta does not matter. When I boycott usually the thing disgusts me and any revenue less for them and more for their competitors especially in regards to how I act (consume) is important to me. Because its my actions. Like there is a lot of indication that the plastic recycling I do likely does not get recycled, but im still going to stubbornly do it. If I was in europe I would totally do the buy european. Will it change what trump is doing, unlikely, but it will help europe gdp over us.