I am bothered by comparisons of apples and oranges, particularly if the point of the comparison is to prove that apples should be peeled because oranges should be. It doesn't even matter if I disagree with the central premise of the comparison; I still want a better analogy.
South Africa is mooting the idea of banning all Internet porn. We could argue all day about freedom of speech or the idiocy of believing that it could be done, but what I actually take issue with is this quote by Deputy Minister of Home Affairs Malusi Gigaba (from this BBC article), to whit:
"Cars are already provided with brakes and seatbelts [sic]... There is no reason why the Internet should be provided without the necessary restrictive mechanisms built into it."
No. No no no. It won't do, Mr. Gigaba. Cars are provided with brakes and seat belts for good reason, and perhaps the Internet of South Africa should be provided with a mythical porn-blocking filter for good reason too, but those reasons aren't the same.
According to Mr. Gigaba, brakes and seat belts are "restrictive mechanisms," possibly because they restrict the car's movement or the movement of the driver. But a far better way to classify them would be as safety mechanisms, in that without them, the car is extremely unsafe, as is the driver. Comparing that safety to a virus scanner or a firewall is kosher, because those things are safety devices for computers and the Internet. If South Africa were planning to put up a national firewall to keep out attackers (rather, of course, than keeping out porn, which isn't so much a safety issue as one of those "restrictive mechanisms") then it would be a fine metaphor to use.
However, what Mr. Gigaba is actually talking about is the technology to keep a car from exceeding the speed limit. That's restrictive technology, and one could argue whether or not it was safer. Similarly, keeping computers from visiting pornographic sites is restrictive technology and one could argue whether or not it was safer. Sadly, Mr. Gigaba can't use that analogy because the technology to keep cars from driving faster than the posted speed limit, if it exists, is not widely available. We could be developing it, and I think it would save lives, but we're busy keeping people from looking at dirty pictures.
In summary, seat belts don't keep you from doing anything you would otherwise do, and their sole purpose (unless you're a crank who believes that they're terrible) is to keep the driver safe. Porn-filtering technology keeps you from doing something you would otherwise do, and there may be a side effect of making you safer. One is restrictive, one is not. And brakes are just part of the car. Without brakes, a car is no longer a car, it's a poorly-guided suicide missile. No comparison there.