???Who are the Disbelievers???
Anyone who disbelieves in the complete truthfulness of The Qur'an or even one single ayat (verse) from the Qur'an, is a disbeliever and is not a brother or sister to the muslims.
Often as Muslims, we do not fully understand verses, but that is not the same as disbelief. If, however, we deny the truth of what is plain, or claim disbelief or corruption in any ayat of the Qur'an, we are calling the Words of Allah, swt, a lie and are in disbelief, thereby nullifying our Islam, i.e. becoming disbelievers.
The Noble Qur'an Al-Maa'idah 5:86
But those who disbelieved and belied Our Ayât (proofs, evidences, verses, lessons, signs, revelations, etc.), they shall be the dwellers of the (Hell) Fire.
The Noble Qur'an Al-'Imraan 3:85
And whoever seeks a religion other than Islâm, it will never be accepted of him, and in the Hereafter he will be one of the losers.
In addition, Ibn Taimiyah said, "[The following is] a disbeliever: Whoever believes that churches are the houses of Allaah in which He is worshipped or who thinks that what the Jews and Christians do are valid acts of worship of Allaah and obedience to Him and His Messenger, or loves or approves of what they do, or aids them in having such places and establishing their religion, and he does so thinking that is a way of getting closer to Allaah or worshipping Allaah." He also stated, "If someone believes that visiting the Jews and the Christians in their places of worship is an act that brings him closer to Allaah, then he is an apostate."
Fe Aman Allah 
