Although enemies of Ali (A.S) the leader of the faithful – Amir-ul-Muminin – are considered to be illegitimate, Salman al-Farsi was a Shi’ah – despite his parents being fire worshippers. In our present world, Sunnis such as those in Pakistan, are the enemies of the progeny of the Prophet (PBUH) – Ahl-al-Bayt w and their followers. While Sunnis perform marriage in an Islamic way, fire worshippers are considered to be unclean – najis. How can it then be that a person born in a najis, unbelieving – kafir household is regarded Shi’ah, while a child born in a pure – pak – household is regarded as a bastard?
I am distressed that your question shows such a confused understanding of Islam and thank you for the opportunity to clarify this difficulty. Firstly, it is mistaken to say that all Sunnis are enemies of Ahl al-Bayt. Indeed, most of them regard love of Ahl al-Bayt as an essential aspect of their love for the Prophet (PBUH). This is emphasised when Allah tells the Prophet (PBUH),
Secondly, who said that a Sunni born in a Muslim household is a bastard? Children born to Muslim households are legitimate. In fact, the Prophet (PBUH) said that, ‘Every child is born a Muslim and it is the parents who make that child a Jew, a Christian, or a Magian.’
Thirdly, Salman chose to become Muslim. Any atheist or fire worshipper who accepts Islam is considered pure, and no one has any right to talk about their past.