i dont imagine any of the cases have ruled that the government can not legislate against child porn, so there's always going to be some amount of both speaker and content speech limits.

they could also just ignore any scotus rulings they dont like, and assert states rights over the topic

Speech rights have never been considered absolute. At most they require strict scrutiny for a government interest to be overcome. Obscenity is in the category that gets the least deference. Political speech gets the most, as "the highest wrung". If all speech got the same deference as the least scrutinized (e.g. child porn) then 1A would be neutered.