It’s not exactly true to say that the Baháʼí Faith is the only religion to have never split.

One Baha'i critic stated the following in a comment on Youtube:

It’s not exactly true to say that the Baháʼí Faith is the only religion to have never split. This is for two reasons: 

1.) The Baháʼí Faith has split. First there was the Bahá'í–Azali split in 1863 (there are still a few thousand Azalis around, mostly in Iran and Uzbekistan). Then, in 1939, the Caravan of East and West severed its ties with the Baháʼí Faith (they still exist and operate an adult-education Italian language school in New York). In 1960, the Orthodox Baháʼí Faith split and has continued into the 21st century with two or three groups numbering around 200 collectively, mostly in the United States and India. There’s also Unitarian Baháʼís, Free Baháʼís, the Reform Bahá’í Faith, the Baháʼís Under the Provisions of the Covenant, the Tarbiyat Baha'i Community, the Universal Faith and Revelation of Baháʼu'lláh, and the House of Mankind and the Universal Palace of Order.

2.) If the Baháʼí Faith has never split, then lots of other religions also haven’t. The Druze faith hasn’t. Scientology hasn’t. Mandaeism hasn’t. Yazidism hasn’t. Ayyavazhi hasn’t (there are 2.7 million more Ayyavazhis in the world than there are Baháʼís). There are probably hundreds of religions that could claim, by this reasoning, to have never experienced a split.

https://www.youtube.com/watch?v=wL5Uc3Y2kv0&lc=UgyckIuP7cjcLJq-ikN4AaABAg