Religious persecution must be done on State-sanctioned grounds (like an official religion or a theocratic state based on Constitution). Any other persecution could just be a particular party's policies e.g. Tomorrow a Buddhist party could come to power in Bangladesh and persecute, say Jews. That does not have Constitutional sanction. Next week a different party might persecute a different religion.

> Sri Lankan Hindu Tamils being prosecuted in Shri Lanka.

And 4 lakh Hindu Tamils were given asylum in India in past 40 years. Proof - https://twitter.com/PIBHomeAffairs/status/120730426394626867... Currently there is no persecution going on there as civil war is over. If in future, they get ill-treated again, a new version of CAB might be brought.

There have been many instances of citizenship granting based on particular cases throughout India's 70 year post-independence history. This CAB is just one of them. It's neither the first, nor last.