“9.334. But to serve Brahmanas (who are) learned in the Vedas, householders, and famous (for virtue) is the highest duty of a Sudra, which leads to beatitude.” –Manu Smriti
“All your talk is of caste and creed
Is it even as natural as the spider and its web?
The four blessed Vedas, were they created by Brahma?
Is caste and creed worthwhile, ye elders of Paichalur?” -Uttiranallur Nagai
(This post mostly consists of quotes from Manu Smriti and Medieval Hindu Bhakti poems, so if you want to skip my spiel just hit the “read more” link at the bottom.)
People in the west tend to have an odd outlook on the ethics or “doctrines” of Hinduism. In most religions, doctrine works something like this: There is a core text, or set of texts, which contain precepts. Early in the religion’s history some sages write commentaries on these. The rest of the reasoning and doctrine formation of the religion continues by referring to these sources for legitimacy. Innovations occur, but normally only if it can somehow be “textually justified.”
Certainly there is a part of the Hindu religion, which operates very similarly to this—the religion of the Brahmins. But Hinduism cannot be thought of as just that. It is the religion of all Indians, except perhaps those who explicitly decry the label, like the Buddhists, Jainsm and Sikhs (and even those divisions are sometimes blurry. Even some sects of Islam are pretty heavily syncretized.)