In the US, according to the U.S. Equal Employment Opportunity Commission, harassment in the workplace (my emphasis)
...is a form of employment discrimination that violates Title VII of
the Civil Rights Act of 1964, the Age Discrimination in Employment Act
of 1967, (ADEA), and the Americans with Disabilities Act of 1990,
(ADA).
Harassment is unwelcome conduct that is based on race, color,
religion, sex (including pregnancy), national origin, age (40 or
older), disability or genetic information.
Harassment becomes unlawful where 1) enduring the offensive conduct
becomes a condition of continued employment, or 2) the conduct is
severe or pervasive enough to create a work environment that a
reasonable person would consider intimidating, hostile, or abusive.
Anti-discrimination laws also prohibit harassment against individuals
in retaliation for filing a discrimination charge, testifying, or
participating in any way in an investigation, proceeding, or lawsuit
under these laws; or opposing employment practices that they
reasonably believe discriminate against individuals, in violation of
these laws.
Petty slights, annoyances, and isolated incidents (unless extremely
serious) will not rise to the level of illegality. To be unlawful, the
conduct must create a work environment that would be intimidating,
hostile, or offensive to reasonable people.
Offensive conduct may include, but is not limited to, offensive jokes,
slurs, epithets or name calling, physical assaults or threats,
intimidation, ridicule or mockery, insults or put-downs, offensive
objects or pictures, and interference with work performance.
Harassment can occur in a variety of circumstances, including, but not
limited to, the following:
• The harasser can be the victim's supervisor, a supervisor in another
area, an agent of the employer, a co-worker, or a non-employee.
• The victim does not have to be the person harassed, but can be
anyone affected by the offensive conduct.
• Unlawful harassment may occur without economic injury to, or
discharge of, the victim.
From https://www.eeoc.gov/laws/types/harassment.cfm
IANAL (I am not a lawyer), but it appears, from your description, that you could be suffering from workplace harassment in several different forms and your workplace could be in violation of several different federal laws. Your state may also have laws that compliment these federal laws.
Your employer should have safeguards in place in the form of handbooks for clients and staff, disciplinary procedures for violators, and grievance processes for staff. These will be required both by law and by the employer's insurance policy that covers the workplace, the clients and the staff for forms of injury and liability.
If your workplace supervisors are not responsive to the incidents of harassment (and it appears they are not):
1) I suggest you contact the civil rights commission in your state, and talk to pro-bono law clinics if you can't afford a lawyer, though many lawyers will take an initial look into a case at no charge.
2) Start to record in written form - and audio and video, if you safely can - these incidents of harassment for use as evidence. And write down past incidents as you remember them.
And, as pointed out above:
Anti-discrimination laws also prohibit harassment against individuals
in retaliation for filing a discrimination charge, testifying, or
participating in any way in an investigation, proceeding, or lawsuit
under these laws; or opposing employment practices that they
reasonably believe discriminate against individuals, in violation of
these laws.
So if you are harassed by your employer for confronting him/her over the harassment from clients, that's a separate incident and possible violation of law, too. Record those incidents, too.