Luke's Ambivalence Towards Judaism
Joseph Tyson tries to get a handle on the question of Luke's ambivalence towards Judaism, and to account for the pro-Jewish side he finds the answer in a late dating of the gospel (c. 120 CE). "Luke rejected Marcion’s theology, and, to counteract his influence, he stressed the connection of Jesus and his apostles with Jews and Judaism." Even aside from the unlikelihood of a late dating, an explanation like this doesn't cut it for me. In listing the anti-Jewish texts of Luke-Acts, Tyson curiously has nothing to say about the strongest one of all: Lk 4:28-30, the only occasion in all of the synoptics (let alone Luke) where the Jews try to kill Jesus apart from general plotting which leads to his crucifixion. The only parallels to Lk 4:28-30 are found in John's highly sectarian gospel (Jn 5:18, 8:59, 10:31), and with Philip Esler I think Luke was also sectarian.
Once we appreciate Luke's sectarian outlook, there's little need to draw on heresies like Marcionism to account for his pro-Jewish retentions. If Esler is right that the Lukan community was made up of Jews and Gentile God-fearers who had been painfully excluded from the synagogue, then the fierce ties to Judaism make perfect sense. Luke becomes a parochial version of Matthew, reverent of the Torah for more isolationist reasons. Unlike Matthew who wanted to re-Judaize Christianity as much as possible, Luke wanted to legitimate its development out of Judaism as much as possible -- and his general strategy was to show that Jesus respected the law for Jews as much as he transcended it for pagans. Judaism thus becomes a legitimate faith carrying within itself the seeds of its own transformation. Unlike the Matthean community which was deviantly and nastily competitive (but not apostate or sectarian), the Lukan Christians were no longer part of the synagogue, in no small part because they followed the same practice as the Pauline and Markan communities which put them beyond the pale: mixed table-fellowship. (The Mattheans, following the authority of Peter (Mt 16:18; Gal 2:11-14), refused to engage in such practice, as seen in the way Matthew revises his Markan source in Mt 15:21-28/Mk 7:24-30; so Esler, Community and Gospel in Luke-Acts, p 92; it's one of Luke's greatest coups that he was able to claim the support of Peter and James by reversing their historical roles.) The Mattheans adhered to the Torah in the context of messianic renewal, and they retained ties to the synagogue by the skin of their teeth. The Lukans, Jews and God-fearer's alike, also respected the Torah (far more than Paul and Mark), but they allowed for its transcendence in ways that made them cast-outs.
The way I see it, Luke was pro-Torah like Matthew, but also sectarian like Paul, Mark, and John, and it's the relationship between these two that defines our answer to the question of Luke's ambivalence towards Judaism.