[The Ruling on One who is Hostile to the Scholars or the Seekers of Knowledge]

Answer: The causes of enmity are varied. If what called to the enmity and brought it about was the narrow temperament of the believer or the scholar, or his sharp nature, or his heaviness, or the like, then one looks at the enmity: if it is in the heart only, without [manifesting by] the tongue or the hand, then there is no harm in it.
But if it is by the tongue or the hand, then it is permissible from him to the extent that matches the harm that has reached him, due to His saying, exalted is He: "And the recompense of an evil is an evil like it; but whoever pardons and makes reconciliation – his reward is with Allah…" [al-Shura: 40–41]; and patience and forgiveness are better, due to His saying, exalted is He: "And whoever is patient and forgives – indeed, that is of the matters [requiring] resolve" [al-Shura], and: "And that you pardon is nearer to righteousness…" [al-Baqarah:237], and other such verses.
But if what called to the enmity and brought it about is nothing other than knowledge, or faith, or seeking knowledge – and were it not for that, the enmity would not have arisen – then it is disbelief (kufr), because it is enmity towards Allah, His Messenger (May Allah bless him and his family and grant them peace), and the religion.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.3