My family is in medicine (doctors and nurses) and I've worked in a hospital too. The only other place where I've seen people treated worse was retail. I've seen patients and their families treat their doctors and nurses like absolute crap.
They think just because they read something on the internet they know more than someone who went through medical school, residency, internship, and setting up a practice and keeping it. Because of the nursing shortage nurses are expected to take on more patients and do more paperwork. A nurse can be so busy that she's lucky to get a 15 minute break (and then still get called because a patient is calling, or a doctor she was waiting for finally came).
When you have a 12 hour shift, it's not 12 hours it's usually more 13-14 hours depending on how much paperwork you have to finish after your shift. Also there's no concept of holidays. I've worked every holiday except Christmas day. How many professions are there if you make a mistake you can kill someone? Also the money that doctor's and nurses make? Believe me the majority of the ones I know earned their paycheck.
Some people can be seen as bitter, angry, or messed up because you deal with life and death as a job. You are dealing with people who do not want to be there. Patients and families are not always at their best in the hospital. Can you imagine being so emotionally invested in every patient you work with? You can not survive medicine if you work that way.