Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
A tv set could be used for a good or an evil purpose.
However, evil and mischief are predominant in it. It is known in religion that a Muslim should not help a fellow Muslim in sin. Allah says: "Help you one another in Al Birr and At-Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression. (Al-Ma'idah 5:2)
Therefore, since your father does not mind what he watches on tv whether Halal or Haram, we do not consider it permissible for you to buy a television for him even if he asks you to do so, let alone if he does not ask you to do so.
Allah knows best.