Is the person who buys a can of coke off their local shop for a refreshing drink part of the problem?
Their local shop owner is a nice guy who has never killed anyone, bit somewhere in the production and distribution chain people have been intimidated or shot or lives have been made miserable.
Colombia: The Coca-Cola Story
The Pause That Represses? Coca-Cola's Controversies
While I completely agree (we cause suffering without knowing it), I think arguments like these are absurd. In order to avoid being a part of the suffering, one must have perfect knowledge of the causal chains of history or practice extreme asceticism. We have complex lives and finite recourses, the best we can do is to not inflict suffering directly.
This form of argument can be applied to almost anything, even something as seemingly innocent as a well liked, relatively cheap can of carbonated water; although due to it's absurdity, it is frequently trotted out for topical issues like crime, drugs and animal welfare in a vain attempt to kill demand by shaming the buyer.