Again, you yourself beg the question: are images the same thing as speech? Yes.
I'm fascinated. Tell how this can be.
And don't drag kids into this. The subject is adults.
Oh please ... children can be the subject of "Free Speech" too (as long as they're faked). Supreme Court said so. Why can't kids be a part of the discussion?
They listen to radio, watch TV, read billboards, go through their parents' stuff. Given the push in Britain and elsewhere to lower the age of consent, I think minors -- especially including those 13 year old boys of whom you spoke -- initially certainly should be part of any porn discussion.
My own introduction to skin magazines came in first grade. I was what, 7, 8? The 4th (or was it 5th) grader next door would share her brothers' Playboys and we'd play at modeling.
Granted, we're talking '69-'70 Playboys. Pretty tame (and almost classy) stuff on which to imprint. But kids are in, baby. Nowadays, there's no need for sussing out Dad or your brother's secret stash. Girls can get far more explicit notions of sex and being sexy than I did just by watching MTV or going to the movies.
In fact ... if I may be so bold as to get the ball rolling on your compare/contrast of Images and Word where "Free Speech" is concerned ... I'd say one difference between images and speech is that even children can "get the message" from an image well before they are first-grade literate.
Stories of Anais Nin would have been totally lost on me until at least 7th grade, if then. But images of the same story might have had their effect on sight.