You're implying a 9 year old is mature to be online. Or that you're never too young for certain things. As if children know what they're doing.
Also, seems like you don't know a difference between sheltered life and raising your children responsibly.
Yes, I'm implying that a 9 year old is mature enough to be online - if they have guidance and trust their parent. And yes, children are never too young to start trying out things - again, with guidance and a trusted parent, but that doesn't mean constant oversight. You teach children to look both ways before crossing a road, watch them do it for some time, and then you let them go to school by themselves. I don't understand how are they supposed to develop responsibility and self reliance if there's constantly someone watching.
Seems like your idea of responsible is my idea of sheltered.
Internet is a wild west, without parental control where your 9 yo can go your kid is a click away from something that may disturb them for life. And it's your responsibility to protect them before at least they hit puberty. Don't fuckin trust your 9 yo to not go places on the internet, that's insane. That's just taking off the responsibility off your shoulders.