First, the world is not safe. The level of risk may be greater or lesser, depending on where you live and what your resources are, but we are all at some risk of attack from our fellow human beings. While we often use the word "inhuman" to describe particularly awful crimes, the truth is that interpersonal violence is as much a part of the human makeup as love and compassion. In addition, there are numerous other dangers in the world -- disease, natural disaster, a vast potential for accidents -- that further jeopardize our safety.
Second, women are as capable as men of protecting themselves and protecting others when necessary. That both genders buy into the myth that they are not keeps women at a significant disadvantage, because they must place limitations on themselves, such as traveling with a male companion or avoiding certain neighborhoods. Acting in accordance with this myth not only perpetuates a helpless mindset among the female population, limiting their sense of potential as well as their careers and dreams, it also impels men to take foolish risks, particularly men who really don't know how to protect themselves but feel that they must do something nonetheless.
These ideas are from my essay "There Are No Front Lines in Modern Warfare -- Or Modern Life," which you can read here. This essay was adapted from a longer piece called "We Aren't Civilized Yet," which appeared in The WisCon Chronicles, Volume 1, from Aqueduct Press.