פירוש על עבודה זרה 118:4

R. Ashi cites his source, a ruling by R. Judah b. Bava and R. Judah b. Betera. They both hold that a non-Jew cannot just libate a Jew’s wine and thereby make it prohibited. The Tosafot say that Rav Ashi is not actually ruling like R. Judah b. Bava and R. Judah b. Batera. These rabbis allow the wine to be sold to anyone. From here R. Ashi deduces that while the other rabbis would not let the wine be sold to anyone, they would allow (or mandate) the non-Jew to compensate the Jew for his loss.
There are stories in the Middle Ages of Christians actually doing this—touching Jewish wine intentionally to cause the Jews a loss. The rabbis responded by allowing Jews to even drink such wine. They did not want this to be a way for Christians to cause massive losses to Jews.