The answer is: the people he studied being part of a larger preexisting colonial system.
Evan based his historical research using humanistic approach in seeing the result of the colonial system. This would make him become much more likely to focus on the suffering that experienced by the target of colonial system.
Despite his intention, being too focused on the perspective of a single group would most likely create a defect in his opinion on how the historical events during the colonial era unfolded. This is why he was criticized by many experts on similar field.
