It was largely just the Jewish people who viewed the Samaritans with disdain.

So let's talk about who the Samaritans were (and actually still are). They were a group of people who were descended from the residents of the ancient kingdom of Israel. They claim to be primarily descended from the tribes of Ephraim and Manasseh.

After the Assyrians conquered Israel around 740 BCE, Tiglath-Pileser III started a series of forced relocations of the Israelites. Over 20 years much of the population was moved to different parts of empire. This was intended to pacify and assimilate the moved population.

The Samaritans were the people who were left behind when everyone else was dragged off, perhaps mixed with people who were moved into the area.

A century and a half later, the Judean kingdom centered on Jerusalem had pretty much the same thing happen to them, and they were carted off to Babylon. But in the case of the Jews the exiles were eventually allowed to return. These exiles mixed with the Jews who stayed behind, and the resulting culture and religion basically became what we know as Judaism today.

The Samaritans weren't included in this new culture. They were close cousins, but with some significant differences. They worshiped YHWH. But they didn't believe in the temple. Their center of sacrifice was Mount Gerizim, not Mount Zion in Jerusalem. They also had a separate version of scriptures which eventually became the Samaritan Pentateuch. To the Samaritans the Jews were heretics corrupted by their time in Babylon. And the Jews considered them heretics right back. For the next several hundred years the two groups competed for who would define what was proper YHWH worship. It became an ethnic and religious rivalry that more than once broke out into violence.

For an equivalent, imagine that Jesus had been born in 18th century London. He may have entitled his parable, The Good Irish-Catholic or maybe The Good Papist rather than the Good Samaritan.