In the Name of Allāh, the Ever Merciful, the Bestower of Mercy
Answer: [Your] attending the sittings of the scholars of Ahl al-Sunnah wa-al-Jamāʿah and benefiting from them is considered to be from good actions, so your father does not have the right to prohibit you from them. Call your father with wisdom and forbearance so that he may accept it (i.e. attending the sittings of the scholars).
If he is upon other than the way of Ahl al-Sunnah wa al-Jamāʿah, then advise him and clarify to him with evidences that the way of Ahl al-Sunnah is the truth, and that it is the way the Prophet (ṣallal Allāhu ʿalayhi wa-sallam) and his companions (raḍī Allāhu ʿanhum) were upon, and that it is obligatory that we take it [as a methodology], stick to it, and abandon everything that opposes it [i.e. the methodology of Ahl al-Sunnah]. Likewise, beware of falling short with regards to being dutiful to your father and showing him kindness, strive against your soul for this, and you will be rewarded in shāʾAllāh for being dutiful to your father and wanting good for both yourself and him.
The Permanent Committee for Islamic Research and Fatāwá
Source: al-Lajnah al-Dāʾimah li-al-Fatāwá: Fatwá: 18190
Translated by: Munīb al-Ṣumālī