I take it to mean that they cannot be treated as someone else's equals. Am I right or wrong?
Not a teacher.
It's not really about if any two prisoners are "equal." (Whatever that may mean.) It is that you can not simply have policies and rules that are universal. For example, some prisoners might be trusted enough to work in a kitchen or library by themselves. Others need to be kept isolated because of their violent behavior.
Some white collar criminals are kept in minimum security federal prisons that are similar to country clubs. Other violent prisoners are in maximum security prisons in 23 hr/day lockup. It all depends on the crime.