As for his statement:
“Abū Bakr was a teacher of children in the pre-Islamic period.”
Even if this report were true, it would not discredit him. Rather, it would show that he possessed knowledge and understanding. A number of Muslim scholars (1) taught children, including Abū Sālih, the associate (2) of al-Kalbī, who taught children, and Abū ‘Abd al-Rahmān al-Sulamī, who was among ‘Alī’s closest companions.
Sufyān ibn ‘Uyayna said: “Al-Dahhāk ibn Muzāhim and ‘Abd Allāh ibn al-Hārith used to teach children without accepting payment.” Others included Qays ibn Sa‘d, ‘Atā’ ibn Abī Rabāh, ‘Abd al-Karīm Abū Umayya (3), Husayn al-Mu‘allim, who was Ibn Dhakwān, al-Qāsim ibn ‘Umayr al-Hamdānī, and Habīb al-Mu‘allim, the client of Ma‘qil ibn Yasār.
They also included ‘Alqama ibn Abī ‘Alqama, from whom Mālik ibn Anas narrated, and who had a school in which he taught.
They also included Abū ‘Ubayd al-Qāsim ibn Sallām, the imam whose scholarly authority and merit were unanimously acknowledged. What, then, if this (4) is an outright fabrication?!
Indeed, even if al-Siddīq had been among the lowliest before Islam, that would not discredit him. Sa‘d, Ibn Mas‘ūd, Suhayb, Bilāl and others were among the downtrodden. The polytheists asked the Prophet, may Allah bless him and grant him peace, to drive them away, but Allah forbade him to do so and revealed: