How can one reconcile filial piety with negative feelings towards the father's marriage shortly after the mother's death?

The right of the mother remains through supplication for her after her death. As for the father, his presence is a blessing and an opportunity to attain righteousness from him, especially in his old age, for he is the middle gate of Paradise, and disobedience to him necessitates entry into Hellfire. Allah has commanded kindness to parents and not harming them, especially in old age. One should seek an excuse for the father in marriage and assist him in it, for an elderly man needs someone to care for him, as indicated by the story of the wife of Hilal ibn Umayyah. The father must be advised with wisdom and gentleness if something inappropriate issues from him. One must maintain ties with him and care for his wife; beware of harshness and disobedience.