We focus on the belief that one’s own partisan identity is rooted in fundamental moral values, beliefs about right and wrong, and so on. Research on “moral conviction” in psychology strongly suggests that intolerance and inflexibility toward those who disagree (and a willingness to reject democratic outcomes that differ from one’s own preferences) is rooted in a tendency to moralize one’s preferences.

Opinion | Political Scientists Want to Know Why We Hate One Another This Much
What does the rise of partisan sectarians portend for the rest of us?