The answer is "wanting to disguise the truth they have uncovered." Some historians find this tough. One of the reasons would be because not all people may or may not, like the truth. Some historians would omit some part of the truth to keep violent reactions from the readers or outsiders.
This was a labor protest rally that
took place near the Haymarket Square in Chicago but turned chaotic after a bomb
was thrown at the police. As a result, people died as a result of the violence
