In the case of Maycomb, the fictional setting of To Kill a Mockingbird, things have always moved slowly and a willingness to accept change is certainly no different.
Maycomb was an old town...
People moved slowly then... A day was twenty-four hours long but seemed longer. There was no hurry, for there was nowhere to go... nothing to see outside the boundaries of Maycomb County.
In the 70 years since the end of the Civil War, little had changed to alter the Southern perception that Negroes were still an inferior race. Republicans were a raritiy in Alabama, as they were throughout the South, and political and social change moved more slowly than other aspects of life. Atticus knew that Tom could not be acquitted. He tells his brother Jack that
"The jury couldn't possibly be expected to take Tom Robinson's word against the Ewells...
"Before I'm through, I intend to jar the jury a bit--I think we'll have a reasonable chance on appeal, though..."
Atticus knew his neighbors well, and he realized that Maycomb was not yet ready to accept a black man's word over that of a white man. His only hope was that somehow the equally unchanging aspect of the court system would save Tom on appeal.
"Why reasonable people go stark raving mad when anything involving a Negro comes up, is something I don't pretend to understand."
It's difficult to challenge set beliefs exactly because they are set beliefs. When a society has held a certain belief for a long time, ther's no way it can be done away with quickly and any attempt to challenge it will be resisted.
Examples of this in the real world can easily be seen:
- Gay rights. Almost all of the opposition to this in the US comes from religious groups. Religion is a set belief and the set beliefs of many Americans make it hard for gays to be treated equally.
- Women in the military. The idea that women cannot function in combat is largely a set belief based on the old days when combat was about physical strength and women were also believed to be mentally/emotionally weaker than men.
There are many other examples of this, but the point is that it will always be hard to convince people to go against beliefs that have been held by society for a long time.
What a great question. There are many thing to say, but let me focus on the nature of common sense.
The taken for granted nature of common sense resists the idea that common sense is localized. Therefore, there is an impulse that wants to totalize and universalize. To put it another way, there is a conviction that things are just the way they are; it always was and always will be. From this point of view, common sense is more dogmatic than religion or science. So, if a people thinks that it should be a certain way, then it will be extremely hard to change opinions. See the link below on a longer text on common sense.