They have shown up whenever women rallied against sexual violence and gender biases in South Korea. Dozens of young men, mostly dressed in black, taunted the protesters, squealing and chanting, ¡°Thud! Thud!¡± to imitate the noise they said the ¡°ugly feminist pigs¡± made when they walked.

¡°Out with man haters!¡± they shouted. ¡°Feminism is a mental illness!¡±

On the streets, such rallies would be easy to dismiss as the extreme rhetoric of a fringe group. But the anti-feminist sentiments are being amplified online, finding a vast audience that is increasingly imposing its agenda on South Korean society and politics.