Note: this question does not deal with WHY the Jews shunned Samaritans. Rather, it questions the extent to which such shunning actually took place in the Biblical and historical records.
In the Gospel of John the narrator tells us "Jews have no dealings with Samaritans" in explaining why the Samaritan woman is surprised when Jesus ask her for a drink of water. But other Gospels and the historical record seem to tell a different story.
In the Parable of the Good Samaritan (Lk. 10) Jesus tells a tale about a Samaritan traveler who rescues a robbery victim by taking him to an inn located in Judean territory between Jerusalem and Jericho. Although the story is fictional, the setting is normal: a Samaritan is traveling between Jerusalem and Jericho, and he engages in commerce with an innkeeper. Admittedly this Samaritan is a special case, but his journey itself is not extraordinary - nor, apparently, is his dealing with the presumably Jewish innkeeper. What is special in this parable is the Samaritan's acting as a true "neighbor," not his interaction with Jews per se.
Historically, Samaria and Judea were both under the rule of King Herod, who conducted large building projects in Sebaste and Caesaria there. A Jew himself (though an ethnic Idumean) he must have relied on both Jewish and Samaritan laborers and craftsmen, who would have needed to work cooperatively.
Moreover in about 27 bce, Herod married the Samaritan princess Malthace, to whom two of his heirs were born. Thus, marriages between Jews and Samaritans were known to occur at the highest level of society and may well have be conducted among the lower classes as well, even if not with priestly approval.
Looking at a map of the area, we see that the most direct route from Galilee to Jerusalem is through Samaria. As merchants and pilgrims made this journey and returned home they must have stopped for water, food and probably overnight stays in Samaritan inns or homes. Jesus' own family is reported to have made such a pilgrimage every year (Luke 2:41) - a journey of several days each way. Certainly other pious Jews would have done so by the thousands. It seems impossible that these travelers would walk or ride their animals through scores of miles of Samaritan territory without having anything to do with the residents or merchants on their way.
According to the Jewish Encyclopedia, Samaritans participated in the Bar Kochba Revolt showing that, given the right circumstances, Jews and Samaritans could join forces against a common foe.
To be sure, there is ample evidence that Samaritans in Jesus' day were despised by many Jews, especially the guardians of racial/ritual purity such as priests and Levites (the villains of Jesus' story) as well as in rabbinical tradition. There is also evidence of violence against Jewish pilgrims on the road through Samaria. But it seems this did not stop pilgrims and merchants from making the journey, any more than news of murders and kidnappings in Mexico stops north Americans to make the trip tough such dangerous areas.
So the question: Is John overstating the matter (using hyperbole) when he says the Jews have nothing to do with Samaritans?