There's some fairly direct experimental evidence supporting your hypothesis that people's causal judgments are influenced by judgments of wrong-doing. Joshua Knobe (dscussed here) concluded from his research in the area that

causal attributions are not purely descriptive judgments. Rather, people's willingness to say that a given behavior caused a given outcome depends in part on whether they regard the behavior as morally wrong.

But, it's not clear that the broader pattern (never mind BP for a moment) represents a mistake. In Cause and Norm <pdf>, Knobe and Christopher Hitchcock argue that the point of the concept of one particular event causing another is to pick out appropriate targets for intervention.