One only has to consider that the vast majority of Baha'i also come from those conflicting belief systems, they will still maintain faith in their past religion, but will have also now embraced all the other faiths as well.
Ah, really? If they are "conflicting" how can they come to believe in all of them? What I think is happening is that they convert and accept the Baha'i teachings of why there are "apparent" conflicts between the different religions.
A former Christian will no longer believe that Jesus is the only way or that he rose physically from the dead or that there is a real hell or Satan.
A former Jew will no longer follow the laws of Moses, like the Sabbath, but will follow Baha'i laws.
A Hindu will no longer believe in reincarnation or an ascetic lifestyle but follow the beliefs and practices of the Baha'i Faith.
Which is how it should be... if the Baha'i Faith is the new truth sent down from the one and only true God. And part of that "truth" from God is that people added in traditions of men and the leaders misinterpreted the teachings of their messenger, and that is how and why there are conflicting beliefs in each religion. So no, they don't believe in their old religion like they used to.