And here is a modern orthodox perspective on intermarriage:
In a lecture at Yeshiva University in 1988, Rav Aharon Lichtenstein unequivocally stated his opposition to retaining ties with a family member who has intermarried. He explained that a Jew who has chosen to intermarry has “crossed a Rubicon” and has turned his back on the Jewish people, whose survival depends on Jews marrying Jews and raising Jewish children who will continue the heritage of our ancestors.
Rav Yechiel Yaakov Weinberg (Teshuvot Seridei Eish 2:6 in the original edition) says that one who has married a non-Jewish woman, whom we certainly according to Halacha are obligated to excommunicate to discourage such behavior, has the status of one who has been excommunicated.