This research is the first to examine the effects of moral versus practical pro-attitudinal advocacy in the context of self-persuasion. We validate a novel advocacy paradigm aimed at uncovering why moral advocacy leads to polarization and proselytization. We investigate four distinct possibilities: (1) expression of moral foundational values (harm, fairness, loyalty, authority, purity), (2) reliance on moral systems (deontology and consequentialism), (3) expression of moral outrage, (4) increased confidence in one’s advocacy attempt. In Study 1 (N = 255) we find differences between moral and practical advocacy on the five moral foundations, deontology, and moral outrage. In Study 2 (N = 218) we replicate these differences, but find that only the expression of moral foundations is consequential in predicting attitude polarization. In Study 3 (N = 115) we replicate the effect of moral foundations on proselytization. Our findings suggest that practical compared to moral advocacy may attenuate polarization and proselytization. This carries implications for how advocacy can be re-framed in ways which minimize social conflict.