What is the ruling on one who says: "Whoever wants to demolish, let him cast doubt upon the Sunnah"?

This phrase, and similar ones said by preachers and defenders of the Sunnah, means that if the people of misguidance wish to destroy the religion and are unable to impugn the Qur'an, they resort to impugning the Sunnah and casting doubts upon it, thinking that this will deceive some of the common Muslims. The goal is to warn against this group, expose its plot, and urge people to defend the Sunnah and adhere to it. Abu Ya'la said: "Indeed, they only impugn the Messenger of Allah (peace and blessings be upon him) and his Companions because we only came to know Allah, His Messenger, the Qur'an, good and evil, and the Hereafter through the narrations (athar). And the Qur'an is more in need of the Sunnah than the Sunnah is of the Qur'an."