Online hate speech has become a pressing issue in the era of information and communication technologies. This study examines the psychological roots of prejudice in online hate speech from the perspectives of contact theory and intergroup competition theory. By analyzing social survey data collected from 1,000 Korean online users in 2022, this study finds that social network size and online hate speech experiences influence prejudice, emphasizing how interactions and perceived competition shape attitudes toward out-groups. According to the results, social network reduced prejudice against people from different regions or with different religions, but increased prejudice against groups perceived as competing for resources, such as immigrants or feminists. These findings show that the mechanism linking contact and hate may vary depending on the specific context -particularly in the context of resource competition. At the same time, they suggest which groups are at risk of becoming targets of prejudice in contemporary Korean society. These findings suggest that eliminating hate requires more than intergroup interactions or policies alone; addressing underlying existential threats and fostering empathy are crucial.