Should he pray behind someone who says that it is not obligatory for women to cover their hair?
Question

                We live in America and there is a person in the mosque who has a certain status among the Muslims. This man said to the Muslims in the mosque that America is more of a land of Islam than the land of the two sacred mosques. When a journalist asked him a question after an American woman became Muslim and started to observe hijab, he answered that Allaah has enjoined modesty on both men and women, but some Muslims say that women must cover their heads, but he does not believe in their covering their heads. 

My question is: Is what this man says true or false? Please provide evidence. Because many Muslim women here follow what he says about it not being obligatory to cover their heads. If he insists on what he says, is it permissible to pray behind him?.
Praise be to Allah.
      Firstly: 

      What this man says about America being more of a land of 
      Islam than the land of the two sacred mosques is false, and there is no 
      need to produce evidence that it is false, because there is no wise man, 
      let alone any scholar, who would say that America is a land of Islam, and 
      America itself makes no such claim. 

      Secondly: 

      It is obligatory for women to cover their heads according 
      to scholarly consensus, based on a great deal of evidence which includes 
      the command to observe hijab, the clearest of which is the words of 
      Allaah, may He be exalted (interpretation of the meaning): 

      “O Prophet! Tell your wives and your daughters and the 
      women of the believers to draw their cloaks (veils) all over their bodies 
      (i.e. screen themselves completely except the eyes or one eye to see the 
      way). That will be better, that they should be known (as free respectable 
      women) so as not to be annoyed. And Allaah is Ever Oft‑Forgiving, Most 
      Merciful”

      [al-Ahzaab 33:59]

      This indicates that it is obligatory to cover the face too, 
      because the jilbab is lowered from the top of the head until it covers the 
      face and chest. 

      We have explained the evidence for it being obligatory to 
      cover the face in the answer to question no.
      11774, and 
      this evidence applies even more so to covering the head. 

      The scholars differed with regard to covering the face, but 
      they did not differ concerning the fact that it is obligatory for a woman 
      to cover her head and hair in front of non-mahram men. 

      Imam Abu Bakr al-Jassaas said in his tafseer, Ahkaam 
      al-Qur’aan (3/485), commenting on the verse (interpretation of the 
      meaning): “And as for women past childbearing who do not expect 
      wedlock, it is no sin on them if they discard their (outer) clothing in 
      such a way as not to show their adornment. But to refrain (i.e. not to 
      discard their outer clothing) is better for them. And Allaah is 
      All‑Hearer, All‑Knower” [al-Noor 24:60]: 

      There is no dispute that the hair of an old woman is ‘awrah 
      and it is not permissible for a non-mahram man to look at it, just as in 
      the case of a young woman. If she prays bareheaded, then her prayer is 
      invalid, just as in the case of a young woman. End quote. 

      It should be said to this pseudo-scholar and his ilk: This 
      hijab or modesty that you speak of: what is the evidence for it, what are 
      its limits, where does Allaah mention it in His Book or His Messenger
      (peace and blessings of Allaah be upon 
      him) in his Sunnah? If he mentions the verses of hijab, he should be asked 
      to study their tafseer. If he ignores the verses of hijab, they should be 
      mentioned to him, “so that those who were to be 
      destroyed (for their rejecting the Faith) might be destroyed after a clear 
      evidence, and those who were to live (i.e. believers) might live after a 
      clear evidence” [al-Anfaal 8:42].

       Thirdly: 

      What the Muslims should do is respect the Qur’aan and 
      Sunnah, and adhere to the limits set by them, strive to learn their 
      rulings and not accept whatever any charlatan says, especially in these 
      times when there are so many who have the audacity to interpret sharee’ah 
      according to their whims and speak without guidance.  

      Our Muslim sisters have to fear Allaah. Let their example 
      be ‘Aa’ishah, Faatimah, Khadeejah and the first generation of righteous 
      Sahaabi women who hastened to cover their entire bodies when the verses of 
      hijab were revealed, and when they went out they could not be recognized 
      because of the black garments they wore, and their faces could not be 
      seen, let alone their hair. 

      Fourthly: 

      This speaker should be advised and told of the rulings on 
      hijab and its nature from the Qur’aan and Sunnah, and the teachings of the 
      scholars. If he responds, then praise be to Allaah, and this is what we 
      hope for him. If he persists in his attitude, then he should not be 
      allowed to teach or exhort the Muslims. He should not be allowed to lead 
      the Muslims in prayer and they should not pray behind him, rather he 
      should be shunned and forsaken until he comes back to the truth. 

      We ask Allaah, may He be glorified, to guide the misguided 
      Muslims, and to make us steadfast in following His religion until we meet 
      Him.  

      And Allaah knows best.