The dispute.

The dispute between Ryker and the farmers is a common trope in Westerns. The wave of movement from east to west begins with trappers and mountain men. Then came the miners and ranchers. The ranchers in Shane used open range for grazing. Ryker and his family, along with other men were the ones responsible for beginning the process of settling the valley. They drove out the natives, killed dangerous predator animals, built trails and roads, and smoothed the way for less adventerous farmers to come along eventually. Without the ranchers, miners, trappers and such, the farmers would never have been able to make a life with women and children. The range used for grazing wasnt owned by Ryker, but had been used by him for years.

The farmers in this story were not blameless, in my opinion. The only reason they could come into the valley and survive was due to the sacrifice of the ranchers. The Homestead Act allowed unclaimed land to be worked and owned after 5 years. The farmers saw good, fertile land being wasted on raising cattle instead of crops, and decided to settle there.

In a way, this movie also retells the story of European intrusion on Native Americans use of the land. In this case, the ranchers are the natives. They use the land for a single purpose, while the farmers consider themselves to be better stewards of the land because they can get more out of it than just some cattle.

I dont think Ryker was a villain until he hired a gunmen. That act crossed a line that a civilized person should not have crossed. Notice how Callaway did not support gunplay.

This is only a movie. In reality, land disputes did not happen in a vacuum. They often led to violence, but usually because of political corruption, not because of the absence of a lawman, as is the case in Shane.