Having lived in an oppressively religious area (in the American South) this is one of the things I like best about China. It's a relief, compared to how it is in super religious areas.
If I felt like talking to someone about religion I'd have to go out of my way to do it. The urban areas in the South are no more or less religious than the North unless you are in a few cities (portland).
The PRC on the other hand has actively persecuted religions/cults (the Falun Gong are a prime example).
But Falun Gong is 'persecuted'. It is different from other religions. Now, it seems to be an peaceful religion, but Back when it was operating in China, it is not. It seeks political status, motivate its people for illegal activities, and people lost they lives because of it.
I understand you cannot believe me. But ask other Chinese from mainland china, shouldn't be hard to find some if you are in tech industry. (They might refuse to share their opinion because they know the answer might offend you.)
Yeah... that definitely has not been my experience of urban areas in the South (mostly Atlanta, Dallas, and Galveston, assuming the latter two are considered "South").
It's subtle enough that I don't doubt that it isn't particularly noticeable from the inside, but as an outsider it was obvious to me.
Along with the general religiosity, there is also this pervasive assumption that everyone is a Christian that feels rather oppressive. I've only found Utah worse in that respect (the only state where I'm a gentile).
That said, Data is not the plural of Anecdote, and my personal experiences could certainly be far from representative.
Religion is not a taboo in China, as is not welcome.