What term refers to behavior that is morally objectionable?

The term that refers to behavior that is morally objectionable is "iniquity." It specifically denotes actions or conduct that are unjust, wicked, or sinful, often highlighting a deviation from moral standards. Iniquity carries the connotation of an egregious breach of ethics or morality, making it the most suitable choice for the description provided.

In contrast, the other options represent positive moral qualities. "Integrity" refers to the quality of being honest and having strong moral principles. "Virtue" denotes behavior showing high moral standards, and "rectitude" refers to morally correct behavior or thinking. These terms embody positive traits rather than behaviors that would be viewed as morally objectionable. Therefore, the unique nature of iniquity as a descriptor of unethical conduct solidifies it as the correct answer.