The danger of a single side story perfectly captures the idea behind the 'two sides to every story' cliche. The title itself advises us that, based on her experiences and multiple stories of a person or place, it better enhances an understanding of a context/situation.
The danger of reducing other people and cultures deprives them from seeking diverse perspectives, which can help stop the stereotypes and cliches that aren’t true and incomplete.
The crux that Adichie wanted to designate was that, until you learn the enlightenment of two viewpoints or perspectives to a situation, you will not understand how to cease misunderstood interpretation.