From the sunnah of the Wahhabiyya/ the modern day Khawarij, is their hasty declaration of Muslims as Kafirs. Many from their ignorant camp even use takfir against a Muslim like an easy weapon of slander, when they find themselves failing in their self righteous argumentation with Muslims. The Prophet (peace be upon him) counted slander during an argument to be one of the signs of a hypocrite.
But if they were aware of the full extent of what their slanderous mouths earn, they would have kept them shut for good. Unfortunate it is for them that they come from a background of no proper Islamic education. They hold high in esteem the torch of ignorance dressed in the garb of simplicity. Only if they had known what the Prophet (peace be upon him) had declared about the likes of them. For the takfiris in reality make none but themselves the real kafirs.
Hudhayfa reported that the Messenger of God (peace be upon him) said, ‘The only thing I fear for you is a man who recites the Quran until you see its beauty upon him, and who supports Islam until God wills, until he abandons it and casts it behind his back and attacks his neighbor with a sword and accuses him of polytheism[shirk]’. Hudhayfa said, ‘O Messenger of God! Which of the two is closer to polytheism, the accuser or the accused?’ The Messenger of God responded, ‘Of course, it is the accuser’. [Narrated by Ibn Hibban in al-Sahih, 1:282/81; and al Bazzar in al-Musnad, 7:220/2793.]