The amount of disdain for millennials and (big scare quotes) "the internet" seems to be related to 'golden age syndrome'. There's always been this kind of complaining about 'kids these' days, albeit it's much heavier for this generation. I don't think it's what the generation is doing, but the fact that's it's so in their face, and they probably wouldn't have a problem with that outside the fact that it forces them to remember themselves doing the exact same thing in secrecy when they were young. Because let's be honest, people have always been pornographic little perverts since the beginning of humanity. People have fucked out of marriage and before they were adults, created porn and sex toys, and have written downright filthy things since literally before we developed writing (except the dirty stories. That was just oral history at that point). Perhaps that embarrasses them, but I think it has more to do with some odd, older generation idea of doing whatever you want, as long as it's behind closed doors, or the Catholic standard of it not being a sin so long as in public you're repentant and prudish in your presentation.

Either way, I think people are flat out lying when they say their concern is for kids' privacy. Sure, it's an important thing to look out for, and there are dangers about posting some of the things people post, but that's not what they honestly care about.