In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam Ibn Battah [rahimahullaah] said: Know, O my brothers! I have pondered over the reason that expelled a people from the Sunnah and the Jamaa’ah, compelled them to bidah and ignominy, opened up a door of trial upon their hearts and prevented them from the light of truth that enables a person to make good judgements; so I found that [coming] from two angles: [a][Unnecessary] research and debate, asking too much concerning that which is of no benefit- [affairs that are] neither harmful to an ignorant [person] nor beneficial to the believer’s understanding. [b]The other [reason is]: Sitting with [a person] whose Fitnah one is not safe from and [is a cause of] corrupting the heart of the one who accompanies him.
[Source: An Excerpt from ‘Al-Ibaanah Al-Kubraa 1/390. slightly paraphrased]