Generally, a person should not obey his parents’ wish if it is against Torah law; the obligation to honor parents does not override other commands of the Torah. As marriage constitutes an important Mitzvah, perhaps a child in this case is not required to obey his parents’ wish not to marry the woman of his choice.
Ha’Rav Ovadiyah Yosef, in his sefer Halichot Olam, states that if the parents deem the girl or her family unacceptable for substantive reasons, and the marriage would cause them embarrassment, then one must obey his parents and not marry the girl. For example, if the parents disapprove of certain negative qualities they see in the girl or her family, or if her or her family’s religious standards are lacking, and they would thus suffer embarrassment as a result of the marriage, then the boy should obey the parents’ wishes. The Torah states (Devarim 27:16), “Arur Makleh Aviv V’imo – Cursed is he who humiliates his father or mother.” Therefore, if the parents are legitimately concerned that the marriage would bring them and their family shame, due to the negative qualities or poor religious standards of the girl or her family, the boy may not marry her. Ha’Rav Ovadiyah’s ruling is based upon the ruling of the Netziv (a”h).
If, however, the girl he is dating is proper, modest and upstanding, and she comes from a generally good family, but the parents disapprove of the match due to personal or otherwise insignificant factors, the young man should consult with a halachic expert for guidance. Depending on the specific circumstances, it might be permissible in such a case to disobey his parents and marry the girl.