Assalam Alaikum. I heard and know that Abu Haneefah and his companions were known as Ahl al rayy ( People of opinion ). Is it true that many scholars disliked Abu Haneefah and sometimes criticized him? Maybe like Al Thawri, Malik, Ahmad Ibn Hanbal, Ibn Taymiyyah, Ibn Al Qayyim, Ibn Hajar, Al Bukhari and his teacher, Al Shafee' and other major scholars of the deen. I want to verify that, because many sources online say that, and Allah swt says, "O you who have believed, if there comes to you a disobedient one with information, investigate, lest you harm a people out of ignorance and become, over what you have done, regretful."
Jazzakum Allah Khair

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Imam Abu Haneefah an-Nu’maan ibn Thaabit al-Koofi is unquestionably one of the Imams of Muslims, and the scholars agreed on his imamate and his great status.

‘Ali ibn ‘Aassem said: “If the knowledge of Abu Haneefa is weighed against the knowledge of the people of his time, his knowledge would have outweighed it.” [End of quote]

Ibn Al-Mubarak said: “Abu Haneefah is the scholar with the best knowledge of Fiqh among the people.” [End of quote]

Ash-Shaafi’i said: “The people are dependent on Abu Haneefah in Fiqh.” [End of quote]

Ath-Thahabi said: “The Imamate in Fiqh and its minute details are given to this Imam, and this is undoubtedly true. It is absolutely unsound (for someone) to ask for evidence for the existence of daytime. His biography could be compiled in two volumes; may Allah be pleased with him and have mercy upon him. He died as a martyr due to a stomach ailment in 150 A.H.” [End of quote – Siyar A’laam an-Nubalaa’, volume six, pages 390 to 403]

All the Muslim Imams are upon guidance and goodness. It is not permissible for a Muslim to be blindly fanatic, to an extent to hate his Muslim brothers and consider them as misguided.

Ibn Hajar al-Haytami said:

“Ash-Shaafi'i, Abu Haneefah, Maalik, Ahmad and other Muslim Imams are upon guidance from their Lord, so may Allah greatly and abundantly reward them for Islam and the Muslims, and resurrect us with them. Since they are all upon guidance from their Lord, there is nothing wrong with someone to advise others to adhere to any of the Four Schools of jurisprudence even if it is different from his own School and belief, because he has advised him to the truth and guidance.” [End of quote]

It was reported that Shaykh Ibn Taymiyyah said: “Whoever believes that Abu Haneefah and other Muslim Imams deliberately contradict the authentic Hadeeth due to inference or otherwise, then he has said something wrong about them and spoke either out of assumption or desire.” [End of quote]

For more benefit on the status and eminence of Imam Abu Haneefah, please refer to Fataawa 186945, 92321, 341902, 264961, and 245815.

Allah knows best.