I wrote most of this after watching the second Republican Presidential Debate, and re-visited it soon after the first Democratic Presidential Debate ended.
Rigid thinkers believe that conscience requires non-compromise, that any compromise with opponents compromises ones own personal integrity. People who can't imagine compromise are in effect intellectually compromised, which ironically is the only compromise they make - that of refusing to listen or think.
As a psychoanalyst I see these people who have bodies of adults but who refuse to betray their inner two-year-old. This becomes emotional loyalty to a defiant part the self above all else. Otherwise they feel they would be turning their backs on a fundamental but unmetabolized (read compromised) self. We were all once two, and we all have powerful defiant elements in our make-up.
But most adults have evolved, going through the sometimes painful process of inner assimilation and accommodation to the immigrant and disquieting forces of parental and social pressures, ranging from external demands to get along with others to the internal demands of developmental, intellectual, and hormonal maturation. The two-year-old self becomes part of a larger self over time, and gets put into perspective.
Some people, however, are unwilling or unable to evolve. They overlay that archaic self with false layers that look like growth and change, but are not. Their inner two-year-old is not only alive, but remains dominant. As adults, those layers become second nature, and rigid people continue to reject certain kinds of thoughts as dangerous threats to their desperate need for inner stability. So they embrace certainty as strength. The new becomes the menace. George Orwell understood this process in his 1949 book 1984. His characters, much like the 2016 Republican presidential candidates, attack internal and external reality as they chant, "IGNORANCE IS STRENGTH".