Comment by LPisGood

It’s not an argument it’s just a statement of fact. “You can’t do this because I bought it” explains what (you can’t do X without Y) and why (I own Y and can therefore control the use of Y).

Now, it doesn’t explain why the decision was made in the first place to enforce a porn filter as a requirement for using the device, but again - it’s not an argument.

I agree that it doesn’t provide a complete explanation because as you mention, if the child bought their own device there would still be restrictions, but that wasn’t the case being discussed.