I think a very good fundamental of being a parent is not just to tell your kids why "doing this" is bad, but rather SHOWING why it is bad.
This is key. Children are so curious by nature and you need to provide them explanations so they don't go discovering these things for themselves. know a super "Christian" family whose parents are deep into their Church, yet none of their adult children know a thing about the Bible apart from the surface-level stuff. Just about all of the daughters got pregnant out of wedlock. The youngest one (who is old enough to drink) is a confused, suicidal, and anxious young woman. She was EXTREMELY sheltered along with her sisters. She can barely use a computer and has the maturity of a fourteen-year-old.
All these kids are screwed up 'cause their parents didn't teach them shit. They were the Biblical instruction spouted by every Church-Christian parent, but they were never given the Biblical reasoning. They were sheltered from all tech, from bad movies, bad shows, music, video games, et cetera, but it didn't matter because when they came in contact with these "bad" things, they went nuts. Sheltering your child is
worthless if you aren't explaining to them why you're doing it. Don't try to protect them so hard that you won't even broach adult subjects with them.
That said, my parents didn't do a good job monitoring me and they've completely given up on my younger siblings. They're basically the opposite of sheltering and that extreme isn't better.
I want to give my kids all of the firsthand knowledge I have when I inevitably limit their internet use, so they have an idea how dangerous the internet is for a young person. Even if you come out of it, somehow, without getting flashed or molested, your perception can be totally warped and you can fall into the wrong crowd—crowds that can be much weirder and much more degenerate than what you'd find at school.