Some kids adopt an edgy political identity as a form of protest or rebellion. I can see this being the case here, especially if your whole family is particularly left-leaning. Kid wants to feel like he has an autonomy over his own decision making and that he’s not just a carbon copy of you or his siblings, so he becomes as contrarian.

As a teen I was also taken in by extremist political ideology on 4chan, but the thing that snapped me out of that is, surprisingly enough, my curriculum at school focusing heavily on critical thinking and problem solving as essential skills. That’s unfortunately not something that can easily be condensed down into a gift-sized package. I’m sure there are some books out there that can help, but I worry that it might be too on-the-nose or that he might just not like reading much to be interested in dry subject matter like philosophy or political science.

I kind of agree with other posters here that taking a family trip somewhere, maybe not explicitly as a gift for him, but as an experience for all of your children, will expose him to stimuli that drastically differ from the way he currently sees the world, which is influenced by a nonstop stream of fearmongering propaganda and a lack of perspective of what a world outside the town or city he grew up in actually looks like.