Religion and Theology

Ijma or Consensus is one of the four pillars of Islamic jurisprudence. The fundamental basis of any ruling is Quran and Sunnah, however, when there are no examples available from these to sources, then Islam encourages Ijma or consensus based upon reasoning and finally if there is no Ijma, then usually scholars end up reaching a conclusion based on Qiyas. Based on the hadith quoted in the question it appears that the Prophet believed that in fact the Islamic community will not agree to something which is incorrect.

According to Imam Al-Shafi The adherence of the congregation (jamaa) of Muslims to the conclusions of a given ruling pertaining to what is permitted and what is forbidden after the passing of the Prophet, Peace be upon him (Cited in Kabbani, n.d.). Based on his understanding, Ijma cannot be carried out by a layperson instead it is reached by a general agreement after a reasoned discussion between different scholars. Conversely the Quran says the majority does not know (aktharrun nass laa yalamun).

Although the question indicates that there is a contradiction between the Ayah and hadith, but it is evident, that Ijma is not something which can be carried out by any group of Muslim, there are terms and conditions which have to be followed, and the belief of the prophet is reiterated when in his opinion an Ijma can only occur when the consensus is based on facts and reasoning.

The idea of Taqleed is linked to Ijma, in a way that it obligates all the Muslims to follows the reasoned agreement between different scholars of Islamic jurisprudence as long as the Ijma doesnt contradict either Sunnah or Quran. However when discussing the seeming contradiction between Quran and Hadith it becomes apparent that indeed Ijma is something which cannot occur frequently, rather it is a decision which is taken after discussions and debate, while most of the time people are unaware of complex and multifaceted issues, so they have to follow the religious scholars in their best possible decision in the absence of  guidance from Quran or hadith.