Final answer:
Prohibiting a patient from using the telephone violates patient rights in a psychiatric setting, unless there are justifiable reasons for this restriction related to care or safety.
Step-by-step explanation:
The action that violated patients' rights in a psychiatric setting is A. Prohibited a patient from using the telephone. Patients have the right to communicate with others outside the healthcare facility, and restricting this form of communication can be seen as a violation of their rights unless there are specific, justifiable reasons pertinent to their care or safety.
As for the other options, B. In patient's presence, opened a package mailed to patient is generally allowed for safety reasons, and the presence of the patient during this action respects their right to privacy. C. Remained within arm's length of patient with homicidal ideation is a safety measure to protect the patient and others. D. Permitted a patient with psychosis to refuse oral psychotropic medication respects the patient's right to refuse treatment, provided they have the capacity to make an informed decision.