No Bahá'í in the West can be called a Bahá'í unless he is first Muslim

No Bahá'í in the West can be called a Bahá'í unless he is first Muslim (believer in Muhammad's revelation and teachings and the Imams) and a Sunni Muhammadan can never become a Bahá'í unless he becomes first a Shi'ih Muslim. The Sunnis were following a false line, they must recognize their error and accept the Shi'ih truth and then this Revelation. The fact that the Bab is a lineal descendant of Muhammad is sufficient proof for us that the line of the Imam Husayn (son of Ali, son-in-law of the Prophet) was the authentic one. Could the Bab have descended from a line of usurpers? In the light of Bahá'u'lláh's tribute to the Imam Husayn could we doubt it? So must the Jews first become Christians, then Shi'ih Muhammadans, then Bahá'ís.

http://bahai-library.com/maxwell_haifa_notes&chapter=1