There's 2 types of bad people and you see them everywhere.
Overt and covert.
Overts, generally most people can see they are bad (except the people like them and the covert people like them) because they are just open about who they are and treat anyone they see as less than them badly.
Overt and easy to avoid.
Coverts are the problem. People say, that person was mean to me! Others say, but he/she is lovely and always nice to me. That's what coverts want though, to be mean to some because they enjoy it and still be wonderful, and perfect in the eyes of others.
Coverts are the ones that do the most damage everywhere and have the backing of others to keep their victims in line.
One example:
Overt racism, people are happy for others to know they are racist. Easy to avoid and stay away from.
Covert racism. Declaring "I'm not racist" while quietly doing little micro aggressions designed to make people feel bad about themselves, quietly not giving people jobs or giving bad grades or turning them down as tenants without anyone having a clue and when their victims try to point it out, they cannot prove it, they can only know it is the truth.
Now imagine parents like that...
For every obviously bad parent out there, there are many who look wonderful from an outside view but treat their children terribly and lie saying "I'm not a bad parent".