There's kind of an apples and oranges thing here. This particular ruling was a question of whether virtual images of children can fall under the tough child porn laws and the Supreme Court said, "no". Those laws are extremely harsh for good reason, but the Court decided that they should not be applied to situations where no children were harmed. Such images can and probably will be deemed obscene even if they are only of virtual characters. Such images are a violation of Visa's censorship rules (which can be more restrictive than the law, as can any site TOS) and would jeapordize the marketplace here.

This ruling did not legalize virtual images in any fashion or provide them any free speech protection. It just stopped them from being added to a more severe law. I seem to recall that another law had a rider that made such images illegal and cannot recall which one, but it seems to have been done in a way that did not contest the earlier Supreme Court ruling.