I've seen behaviors that are in one society completely acceptable, even part of the culture. Yet, in other societies these exact same behaviors are deemed unacceptable and in need of treatment or a cure, perhaps even punishment.
I guess the guidelines for what is or isn't "normal" are set by society, cultures, even the micro-cultures of neighborhoods, religions and other affilations. The problem comes into play when someone is a member of two groups with opposite views on a particular behavior:
For example - what's acceptable to the micro-culture of a gang member from the inner city, might not be acceptable to the larger cultures of that person's religion, neighborhood, city and country.
Another example - why is nail-biting socially acceptable and yet other "picking" behaviors are not? There are no victims, the individual's health is usually not an issue and the only outcome is cosmetic. Seems the "fashion police" and people hung up on looks and vanity (most of us to a certain degree) are the ones who say this behavior is wrong.
I guess whenever someone has difficulty coping, dealing with life or otherwise functioning in society and the brain is involved, then there is a "problem" that needs to get fixed, or at least lessened in severity.