Imaam Ibn Taymiyyah (died 728H, may Allaah have mercy upon him) stated:
“I am one of those most severe in forbidding that a person in particular should be declared as an unbeliever, an open sinner or a sinful transgressor until it is known that the proof of the Messenger is established upon him, the like of which, if it is opposed one becomes an unbeliever or a sinner or a transgressor. And I affirm that Allaah has forgiven the mistakes of this Nation (Ummah) – and that is general for affairs of belief, sayings and actions.” 
The Jihadists try to use isolated statements of Ibn Taymiyyah to support their positions, but this is a smoke screen set up to deceive the Muslims and dishonour this great scholar. Ibn Taymiyyah also stated clearly that there are legitimate barriers to the declaration of takfeer upon the person who apparently denies the texts:
“It is possible that a man has not heard these revealed texts, or that he heard them but they are not established as being authentic with him, or as far as he sees they contradict other texts necessitating interpretation, even if it is incorrect.” 
 Majmooʿ al-Fataawaa, 3/229.
 Majmooʿ al-Fataawaa of Ibn Taymiyyah, 3/231.