Bahá’u’lláh wrote:

“The Great Being saith: O ye children of men! The fundamental purpose animating the Faith of God and His Religion is to safeguard the interests and promote the unity of the human race, and to foster the spirit of love and fellowship amongst men. Suffer it not to become a source of dissension and discord, of hate and enmity…”
(Gleanings from the Writings of Bahá’u’lláh, p. 215)

‘Abdu’l-Bahá said:

“The third teaching of Bahá’u’lláh is that religion must be the source of fellowship, the cause of unity and the nearness of God to man. If it rouses hatred and strife, it is evident that absence of religion is preferable and an irreligious man better than one who professes it. According to the divine Will and intention religion should be the cause of love and agreement, a bond to unify all mankind, for it is a message of peace and goodwill to man from God.”
(The Promulgation of Universal Peace, p. 181)

“Religion should unite all hearts and cause wars and disputes to vanish from the face of the earth, give birth to spirituality, and bring life and light to each heart. If religion becomes a cause of dislike, hatred and division, it were better to be without it, and to withdraw from such a religion would be a truly religious act. For it is clear that the purpose of a remedy is to cure; but if the remedy should only aggravate the complaint it had better be left alone. Any religion which is not a cause of love and unity is no religion.  All the holy prophets were as doctors to the soul; they gave prescriptions for the healing of mankind; thus any remedy that causes disease does not come from the great and supreme Physician.”
(Paris Talks by ‘Abdu’l-Bahá, p. 130)