You like to keep your goalposts mobile I see. Sure, you personally never said that personal boycotts have material effect. You just think that people should adhere to a moral code because the moral code has a material effect. Or something. It's hard to tell what your actual position is.

Yes, liberation is a global project. But as we have seen, global projects comprise local projects. You must first organize your neighbors. If you cannot organize your neighbors, you cannot organize with people across an ocean (unless you move). You literally cannot be meaningfully "in solidarity" with someone you don't know, can't locate, can't communicate with, and can't have any effect on. You can be psychically in solidarity with them, and believe that praying or self-denial is a form of solidarity, but materially, it's just emotional self-soothing.

If you want to be in solidarity with those child laborers you actually need to do something that puts help them. Researching their stories is not even enough, but it's the first step to being able to tell their stories. Telling their stories to others is the bare minimum step in solidarity with others at a distance. If you're telling stories about consumers failing the moral standard, but can't tell the stories of specific peoples in specific places and specific times, you're attacking your neighbors and defending no one. This is not solidarity.

I guess if someone is distant and exploited enough, it's fine to take part in that exploitation yourself.

Why are you sitting on your ass commenting from devices and exchanging data with servers hosted in data centers so that others get dopamine hits from staying engaged on their devices that exchange data with servers hosted in data centers? Is that fine? Is it fine that you are taking part in that exploitation yourself? Your position is contradictory because you are allowing idealism to supersede materialism.

should you lie about the fact that you yourself won't give up those chocolate bars to your fellow activists, or just to the press?

This is the right place for moral reasoning! If you are organizing against something, actually building solidarity instead of just thinking good thoughts about things, then the moral quality of your behavior and disciplines actually have material effects - on the people you are in relations with. When you are a lone consumer with no relationships to anyone organizing to bring about change, your choices have no effect except on your own self image. But when you enter into relations on a basis of, for example, ending a specific practice, then establishing ethical norms for behavior that signal commitment, at a minimum, is actually quite materially valuable. And even those people who organize against child labor for chocolate have to wear shoes and clothes (and there is child labor in those supply chains), walk streets (and prison slave laborers make the signs), use the internet (and the millions of devices produced with materials that are unethically sources), and live on stolen indigenous land.

It can't be global solidarity with all struggles simultaneously and everyone adhering to moral codes of total self-denial and disengagement. We create our own history, but we do not do so under circumstances of our choosing. We inherit our place in history from the past, and we must make the most effective choices we can to bring about the world we wish to see.

And telling individual people that they are personally morally failing and thus unwelcome and impure because they purchase a few dollars worth of chocolates a month from the retail end of a global supply chain that was built up over several centuries might not be the most effective path to bringing about that world.