In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Ibn Abdul-Barr (rahimahullaah) said:
According to the scholars, Taqleed (i.e. blind following) is other than Ittibaa. That is because Ittibaa is to follow a person based on what is apparent to you based on the superiority of his statement and soundness of his school of thought. And Taqleed is that you speak with his statement, whilst you neither know the angle of his speech nor its meaning and you reject speech besides it; or his mistake is made manifest to you, but you follow him and venerate his opposition (to the truth), whilst the corruptness of his speech is clear to you. This is what is forbidden to speak with in the religion of Allaah (The Most High). [End of quote] 
Al-Allaamah Rabee Bin Haadi Al-Madkhalee (may Allaah preserve him) said:
Indeed, bigoted partisanship and (blind following) of schools of thought in affairs of creed, affairs of worship, politics and other than it has appeared; so what was the stance of the Imaams of Islaam towards those bigoted partisanships and oppressive Pre-Islamic (traits), which split the Muslims and weakened Islaam at the same time?
Indeed, the companions (may Allaah be pleased with them), such as the likes of Abdullaah Ibn Umar freed themselves from the people of bigoted partisanship and desires, as it was narrated by Imaam Muslim (regarding) the time when news reached (Ibn Umar) about those who innovated the doctrine of the negation of Allaah’s pre-decree; so he (Ibn Umar) said:”If you meet those ones inform them that I am free from them and they are free from me”, and what Ibn Umar swore by that ”if one of them were to spend in charity gold equal to mount Uhud, it will not be accepted until they believe in the pre-decree of Allaah.” 
A Misunderstanding Regarding The Statement, ‘Laa Inkaar Fee Masaa’il Al-Khilaaf [There Should Be No Repudiation In The affairs of Khilaaf (i.e. differing)]
Some people are under the illusion that what is intended by this statement is that it impermissible to repudiate (others) regarding any affair in which difference of opinion is held. So based upon this (illusion of theirs), it becomes impermissible to disapprove of a Munkar (an evil) unless there is complete agreement in doing so. This is a wrong understanding which necessitates the termination of enjoining good and forbidding evil.
The scholars (i.e. of Ahlus Sunnah) hold differences of opinion in most of the Masaa’il (i.e. the verdicts on fiqh and subsidiary issues). And what is correct regarding this statement ‘Laa Inkaar Fee Masaa’il Al-Khilaaf- There should be no repudiation in affairs of Khilaaf (differing)’ is that there should neither be harshness in (one’s) disapproval nor (in one’s) criticism regarding those issues about which there is no manifest proof to be taken as the final (verdict). And the basis upon which this is founded is that the issues of khilaaf (differing) are of two categories:
The First Category: They are those issues of khilaaf in which there is proof necessitating that it should be taken as the final (verdict). So here, the proof must be taken and the other statement (or opinion) in opposition is discarded. And whoever follows the statement (or opinion) that is established to be in opposition to the proofs, then he is to be repudiated.
The Second Category: It is those issues of khilaaf in which the proof has not been manifested in order to be taken as the final (verdict). It is an affair in which the evidences contend with each other or the views are at variance. This is an issue of Ijtihaad, and there is neither disapproval nor reprimand against the one in opposition; rather advice is given to acquaint (each other) with the statement that carries more weight. This second category of (khilaaf) is what is intended by the statement ‘Laa Inkaar Fee Masaa-il Al-Khilaaf’ which some people have understood in an unrestricted manner. 
Shaikh Rabee Bin Haadee Al Madkhalee (hafidha-hullaah) said:
We do not say that there are people of ijtihaad amongst ahlul bidah because they are followers of desires, and Allaah and His Messenger have testified to this. The misguided innovator stirs up discord (or splitting) and errs, and then says to you, ‘This is ijtihaad’.
When Hikmatiyaar and the misguided parties (in Afghanistan) murdered Shaikh Jameel Ur-Rahmaan, they said: ‘This is ijtihaad’. Making lawful the spilling of the blood of the Salafis is Ijtihaad to them. This is what it is! They (ahlul bidah) do not fall into an affair of misguidance or a calamity except that they say, ‘This is ijtihaad’. This is diluting Islaam. It is falsehood, misguidance and bidah mixed with truth when the mistakes of the (true and qualified scholars of ijtihaad)- for which they are rewarded- are placed at the same level with innovation about which the Messenger (sallal-laahu-alayhi-wasallam) said that it will be in the fire. 
 [Jaami Bayaan Al-Ilm Wa-Fadlihee: 2/787]
 [Source: Silsilah Ar-Rasaa-il Al-Ilmiyyah Li-Fadheelatis Shaikh Rabee Bin Haadee Al-Madkhalee….page 370]
 [Source: Ibaaraat Moohimah, page 25’ by Shaikh Muhammad Bin Umar Saalim Baazmool (may Allaah preserve him). Abridged and slightly paraphrased]
 Ajwibatul Allaamatush Shaikh Rabee Bin Haadee Al Madkhalee Alaa As-ilah Abee Rawaaha Al-Manhajiyyah; page: 20