How, then, were you able to construct these sentences? (And how was Dr Grandin able to construct the sentences that comprise her book?)
Well, how do you manage to think about abstractions in pictures? What would a picture of truth, or justice, or evil look like? Of course I realize that you could choose to use some picture as a symbol of such a concept -a blindfolded lady with a sword and scales for justice, maybe, or Hitler, or the kid who used to bully you at elementary school for evil - but unless you already had the concepts and chose to associate the pictures with them, the pictures themselves might indicate anything: S&M or Germany or 10 year old boys or, well, anything. You could use a picture of Hitler to represent a bacon cheeseburger if you wanted (but only if you already knew what a bacon cheeseburger is).
Thinking only in mental images won’t get you very far, especially with abstract matters. (Probably animals think in images - not necessarily visual ones - but their lack of language precludes them from thinking about anything very complex or abstract.) You (like Dr Grandin) may be a more than averagely visual thinker, but, as you are obviously capable of abstract thought and the construction of coherent sentences, I take leave to doubt that you think entirely in images, and never have a verbal thought at all.