So what do these two things have in common? I think you can figure that one out. Be creative.
For once and for all, it's just a piece of fiction. It's not based on history. There is no Da Vinci Code, there was no Prieury de Sion before Pierre Plantard - a right-wing ultramonarchist with claims to a Merovingian bloodline - and some friends invented it. The idea was so cribbed from the idiots who wrote Holy Blood, Holy Grail, which built Plantard et al's delusions of grandeur into a pile of wing-nut tinfoil hat conspiracy crap, and the saddest thing is that the focus on this idiotic vision of Mary Magdalen as the earthly vessel of the Lord's sacred seed draws attention away from what the Roman Catholic church really did conceal about her.
If you want to know something really revolutionary and dangerous about Mary Magdalen, read the Gnostic gospels - the ones that were excluded from the biblical canon and ordered destroyed, but have survived in bits and pieces here and their, most notably in the Nag-Hammadi find. The Gospel of Philip is instructive. So is the Gnostic text Mary herself is reputed to have written, called the Gospel of Mary (this one was found in Cairo in the late 1800's, not at Nag-Hammadi).
These excluded Gnostic texts identify Mary as not just one of Jesus' companions, but as someone very special to him - not because she was his lover, although she may also have been that, but because she understood his teachings better than anyone else. One passage of the Gospel of Philip says:
They [the disciples] said to him "Why do you love her more than all of us?" The Savior answered and said to them, "Why do I not love you like her? When a blind man and one who sees are both together in darkness, they are no different from one another. When the light comes, then he who sees will see the light, and he who is blind will remain in darkness."
Mary was the one who set the course of the Christian church after the death of Jesus. It is on her vision that the initial message of the Ressurection rests. Some passages in the Gnostic gospels suggest that Mary was one of the leaders among the early disciples, and considered by at least some to be the person Jesus chose to lead the early church. Mary preached. Mary was, as much as any of the disciples were, a priest, and following her example, other women in the first two centuries of Chritianity were also priests and preachers.
The Gospel of Philip also tells us that there was a power struggle in the years after Jesus' death between Mary and Peter - Peter refused to accept that Jesus would give higher instruction to a woman, but other disciples - Matthew among them - accepted Mary as, at the least, the recipient of deeper instruction from Jesus and thus a legitimate teacher to the other disciples.
Now, let me ask you - what is a more revolutionary secret? That Jesus might have had sex, or that Jesus intended to place the leadership of his movement in the hands of a woman who he believed understood his teachings better than any of the men around him? That Jesus had a child, or that he intended women to have the same authority as men within his church?
Please note: I am not a Christian. I am looking at the history of the accounts of the person we know as Jesus and his companions, at the history of the early Christian movement, and the history of the Catholic Church. Whether Jesus was divine is irrelevant to this discussion; he and his followers have impacted history based on the assumption that he was, and there are many accounts of how that happened. From a historical perspective, there's no difference in legitimacy between the texts that were preserved as part of the Bible, and the texts that were excluded, mostly on grounds of theology and politics.
But if I were a Christian, I'd much rather have the legacy of a woman who was called to lead the early church than a convoluted story about a bunch of men hiding a holy flower-pot.