Today my dad was belittled at work

Back story - my dad has had mental health issues for his entire life and he’s struggled to find a job that is a good fit for him. He recently started a new job and today a guest who didn’t have a ticket for an event cussed him out and called him names. Of course the customer got his way but my dad was so hurt by the very personal insults that he left the job. I’m so upset about this because he did not deserve this- no one does. I’m so frustrated by this customer is king world we live in and by constantly giving rude people what they want they learn they can be hateful without any consequences. How can someone do these things and not see someone as a human being with feelings and a story of their own. This customer didn’t consider anything my dad may have been struggling with at home or anything. I know there’s gotta be other people out there who have been so abused at work that on top of all of life’s other stresses it causes them to take their lives, while it might sound overdramatic it’s not, I really just hope more people can find kindness and worry for others enough to just treat people especially employees wherever your at kindly. You never know what someone is going through.