Who is responsible
The individual who discriminated, asked unnecessary questions on which discrimination could be based, sexually harassed, publicly vilified, or victimised another person, is responsible for their own behaviour. A complaint can be brought against this individual.
If the things complained about happened in the workplace, in the course of a person doing their job, the employer (in addition to the individual) may also be responsible. This is called vicarious liability. An employer will not be vicariously liable if they took reasonable steps to prevent the behaviour.
Anyone who encouraged or requested the behaviour is also responsible, and a complaint can be brought against that individual.