In this quote from James Patterson's "Murder Games," the idea is that what we consider normal or abnormal behavior depends on societal beliefs about the context. When society perceives circumstances as justified, behaviors that might otherwise be seen as abnormal are accepted as normal.
Essentially, the distinction between normal and abnormal conduct is determined by collective perception rather than an absolute standard. If the context supports the behavior’s justification, it is deemed normal; if not, it is regarded as abnormal.