The most hateful thing to a debater is to reject the truth revealed to his adversary and thus he takes to deception and deceit. The Holy Nabi (Sallallahu 'Alayhi wa Sallam) prohibited dispute about useless things. He (Sallallahu 'Alayhi wa Sallam) said:
"If a man gives up disputation in matters of unlawful things, a garden will be built for him in Paradise. If a man gives up disputations in matters of Haqq, a house will be built up for him in the highest Paradise."
Imam Malik (Rahmatullahi-'alaih) states: [this] Debate destroys the 'light' of knowledge.
Mufti Taqi Uthmani: “Even if Argument & Debate are for/on Haqq, abstain from Argument & Debate.”
Maulana Yusuf Ludhianvi Shaheed:
Discussions and debates hamper the ability of a person to carry out (good) actions. It is reported in Musnad-e-Ahmad, Tirmidhi, Ibn Majah and Mustadrak Haakim that Rasulullaah (sallAllaahu alaihi wasallam) said:
“That nation is not led astray after the guidance has been brought to them, except when they are given to arguments.”
Shaykh Ashraf Ali Thanwi
It is written in Malfoozāt Hakeem-ul Ummat, vol. 1, p. 180 that once, in the course of a discussion, Hadhrat Moulānā Ashraf Ali Thanwi said:
The Deobandi, Wahhābi, and Barelwi differences have caused great harm to the ummah. Nevertheless, I do not respond to anyone (to their criticism and allegations). In fact I detest such futile discussions.
Taken from muftisays.com