I believe the decision to allow digitally created child porn proves you correct in why it is banned, but does not disprove my point on why society has a responsibility to ban it.
No matter the method of creating child porn - it doesn't elevate society in the least. People who might cry out on principle to allow the creation of child porn if it doesn not actually exploit children are like people who cry out on principle to allow the consumption of fecal material in the name of individual freedom.
Government exists to restrain evil. That's one of it's G-d given functions. This is true whether or not everyone who is goverened believes in G-d. As a society we have a responsibility to do what we can to identify evil and restrain it so that good will have the opportunity to flourish.
Shalom.