What are the problems a sociologist may face in seeking to interpret objectively the actions of other people?
The problems a sociologist would face in this attempt are the same that would be faced by any social scientist. All social scientists are faced with the difficulty of seeing past their own cultural preconceptions or prejudices.
Sociologists who look at other people look at those people through the lens their own experiences. They have a hard time adopting the ways of thought of the people they are observing. Because of this, sociologists, and social scientists in general, are prone to misinterpreting or prejudging the behaviors of people they observe when those behaviors wouldn't "make sense" in the observer's own culture.
In the link below, scroll down to "Observer Bias."