Places where people perform blasphemy the most are veneto, friuli, lazio, and the ones from toscana (tuscany). The various regions often think they got the best blasphemy, but I think the clear winner is the city of venice, they rank number 1 in the whole world for blasphemy.
Blasphemy is illegal, but is performed by tv commentators, sport people and so on. Some older guys blaspheme 3 times a second, it entered their daily parlance and they blaspheme inside churches, in front of priests, in the schoolyard, pretty much everywhere. Also, blasphemy culture is the first thing that black people learn when they step foot in italy. They learn if they say "porcodio" very often, its supposed to be fun. And indeed it is. Seeing all these young negros saying "porcoddio" is surely a joy to see.
Theres dubbing done to movies adding blasphemy words.
People from rome blaspheme for fun, its fun for them. In my region they blaspheme more like a saying, its a mundane thing. The dialects are quite simple when spoken by the illiterate boomers, so they contain lots of blasphemy and hand gestures. But some dialects are real languages, such as sardinian.
I personally dont speak any dialect, I just know all the blasphemy they do, I find it the best thing in life. I love it, to have this secret code I can use, to be understood while nobody else in the world knows what the fuck im saying. Because, almost none of these words have a translation. In the english lnguage you can only say goddammit and pretty much thats it.