When my kid started out using the internet, it was over-the-shoulder supervision to start out, then slowly dropping to in-the-room supervision (the PC in the living room), and progressively less over time, with the clearly stated proviso that I would occasionally be glancing over history just to make sure he wasn’t getting caught up in anything horrible, but that I wouldn’t be going into any kind of detail. At 13, he got his own PC in his room, and I left him to it.
I’m a very firm believer that you don’t attempt technical solutions to administrative problems. Privacy is important and monitoring is shit. You equip your kid with the tools and the supervised-experience to make good decisions, and once they can balance by themselves you let go of the bike.
Teach them to do dangerous things safely, that’s parenting in a nutshell.
(actually to clear up a misconception: to teach a kid to ride a bike, you hold the shoulders, not the bicycle. With the extra feedback they can actually compensate and learn to balance; if you hold the bike itself it just weirdly fights them and their cerebellum never gets it)
If someone came into my home and started making derogatory racist remarks about me, I’d say that response would be entirely appropriate.