Extremism is a common phenomenon in the political world. Although it is not new, extremism has different sources, emerges in different forms, and on occasion can exercise a disproportional political influence. Among the many concerns about extremists is their lack of tolerance. As Robert Kennedy bluntly stated, the danger from extremists ”is not that they are extreme, but that they are intolerant.” Treating Kennedy's statement as a hypothesis, this study examines the political tolerance exhibited by Taiwan's extreme nationalists-dubbed ”deep-Green supporters.” Utilizing survey data recently collected in Taiwan, this research shows that deep- Green supporters do indeed have lower levels of political tolerance toward groups that are perceived as threatening the values vital to them. The findings not only reveal the underlying dynamics of the extremists' political tolerance, they also have important policy implications for the future development of Taiwanese democracy.