Bullying and harassment happens in a workplace when the upper management does not want to accept the fact that maintaining a positive work environment is one of their responsibilities. Because I believe that if managers/supervisors understand clearly that bullying will not be tolerated, then the environment will be safe for everyone.
It is very important that the owner and/or the CEO sends a very clear message to the rest of the company that bullying and harassment will not be tolerated. Along with that it is also necessary to put together a set of processes and procedures so that any reported incidents of bullying and harassment can be investigated properly. It is also necessary to put together appropriate training programs for all supervisors and managers as well as for all employees to make sure everyone is aware of what is expected in terms of maintaining a positive professional environment.
In larger companies the task of maintaining a positive professional environment is often the responsibility of the Human Resources Department. Most HR personnel these days are well aware of these issues and are typically well qualified to set up processes and procedures and training for handling these matters. However, many small companies do not have HR departments. In those cases the owner may have to get involved with this matter and set up some minimal processes and procedures to handle any reported incidents. The bottom line is that it needs to come down from the top as one of the key priorities for the organization.