Bullcrap. When I was a kid in Texas you couldn’t get a Playboy without a store clerk selling to you. No chance a 12 year old was getting one.
Now a 12 year old can see unspeakable porn on a phone and nobody gets in the way. Texas was much better back then.
And somehow the Founders and nobody up through the next 200 years thought the 1st Amendment protected massive amounts of unspeakable porn.
So you are incorrect. Not a single founding father would have been against this Texas law. If anything they would oppose it as obscenity even after 18.
You are exactly right.