In societies where the populace exhibits a wide range of religiosity, social conservatives (religiously devout or socially traditional) feel their beliefs and way of life threatened, even where others in their society (secular, or socially liberal) have no desire to threaten them, or to discriminate against them, or even to proselytize. Examples include devout English Pilgrims in liberal 16th century Holland and devout Muslims in liberal 21st century Western Europe. We suggest that this is because diversity in religiosity itself poses a threat to conventional personal morality (attitudes on abortion, divorce, euthanasia, suicide, prostitution). The consequences of societal diversity in religiosity (the centrality of religion to one's life) for individuals’ endorsement of conventional personal morality have been neglected in prior research. This paper shows that diversity in religiosity at the national level undermines individuals’ endorsement of conventional personal morality, net of an individual's own religiosity, net of the average levels of religiosity and socioeconomic development in the individual's society, and net of key individual‐level controls. Data are pooled from the World Values Surveys/European Values Surveys, 1981–2008, with 90 countries, 200+ surveys, and 300,000+ individual respondents. Analysis is by multilevel methods (variance components models with fixed effects and random intercepts, estimated by generalized least squares [GLS]).