resentment is directed towards higher-status individuals,
anger is directed towards equal-status individuals and
contempt is directed towards lower-status individuals.
As a native English speaker, I would agree to those definitions. However, as an amateur philologist, I notice that resentment and contempt are Romance derivations and anger is not.
Towards our equals we use English and to our superiors and inferiors, we use French.
"Resentment" means to feel again. Why it has taken on a negative connotation, I don't know. I would like to say that the thought of dachshunds makes me feel resentful, but it sounds wrong to my ears.
Fred states that philosophers 150 years in the future will understand him. Atlas Shrugged is overflowing with resentment. I believe that the equality that Christianity preaches leads to resentment. We are told we are equal, but reality, and Nature, will not be denied indefinitely.
People realize, perhaps at an unconscious level, that equality is a sham (even more so than an afterlife) and that is the origin of the resentment for those who are more successful or intelligent than themselves.