Answer:

     First, the word Imam bears various applications and isn’t restricted on twelve Imams of Shiites; but the Household of the prophet (peace be upon them) are the real successors of the holy prophet (P.H.) and take over all responsibilities of the prophets. The difference is that they aren’t inspired and don’t bring a new religion.[3] Consequently, the Household of the prophet (P.H.) are the greatest guardians of Islam and the most complete leaders and pioneers of the community. Because the prophethood aspect was negated, the word Imam has been used for him in Shiite culture.

     Second, this Baha’i reasoning has been blemished originally because according to the surah Ahzab/40 the prophethood and religions have been terminated:

مَا كَانَ مُحَمَّدٌ أَبَا أَحَدٍ مِنْ رِجَالِكُمْ وَلَكِنْ رَسُولَ اللَّهِ وَخَاتَمَ النَّبِيِّينَ وَكَانَ اللَّهُ بِكُلِّ شَيْءٍ عَلِيمًا (احزاب/40)

     Muhammad is not the father of any man among you, but he is the messenger of Allah and the Seal of the prophets; and Allah is Aware of all things. [Al-Ahzab/40]

     The Muslim community believe and many traditions stated by the Imams (peace be upon them) regarding the finality of the holy prophet (P.H.) indicate that there isn’t any opportunity for a new religion to be emerged in order for a group of people to pose it and misuse.[4]

     Because based on the holy Quran to which Baha’is adduce, the holy prophet of Islam (P.H.) is the terminator of religions and the Al-mighty God has chosen Islam and the eternal religion of human being:

الْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الْإِسْلَامَ دِينًا [مائده/3]

     This day have I perfected your religion for you and completed my favor unto you, and have chosen for you as religion Al-Islam. [Al-Maidah/3]

     So, the holy prophet (P.H.) stated:

"اَیُّها النّاس اِنَّهُ لا نَبِیَّ بَعْدِی وَ لا سُنَّهَ بَعْدَ سُنَّتی فَمَنْ اِدَعی ذلِکَ فَاقْتُلوُهُ وَ مَنْ تَبَعَهُ فَاِنَّهُ فِی النّار..."[5]

     “ O’ people, know that no prophet will come after me and there won’t be any religion after mine. A person who claims prophethood after me, his claim and innovation will be fire (he will invite people towards the hell) kill him not to deviate people. Know that everybody who obeys such claimants will be in the hell fire.”