That’s probably not a popular opinion here, but: parents do not have a right to their child. If the child was cool with this, then that is the important part (and from what I read I’d guess he would be).
Let’s posit it the other way around: a deeply religious pair of parents raises a kid that ends up being strongly anti-religion and comes to some “fame” due to that. Would you describe those celebrating that kid as “cunts” as well? And if not: why?
And no, I’m not religious myself and think a lot of that stuff is stupid and much of it is dangerous, but “those parents deserve better” is an argument that’s used in exactly the opposite way in other areas: to oppress kids that don’t “submit to the norm” that their parents think are best.
Do that two more times after you’ve died and you might have a shot!