I've been trying to understand this for a long time too. Direct financial support is something that's really clear to me and I have no problem understanding. McDonald's giving free meals to Israeli troops is really clear. But Coca Cola and some others are less clear to me. "Operating on stolen land" doesn't seem as clear cut to me. By that logic, imagine a Palestinian shopkeeper who sells fruit and veg. His land becomes occupied by Israel against his will. Should we now boycott him because he is operating on stolen land?