"If it were not for other people's work product and intellectual effort you would have nothing to sell."
If it were not for automobile manufacturers you would have nothing to drive. So what? Where does this line of reasoning take us? To the fact that our anonymous letter writer is a sanctimonious bitch who looks down her nose at those she considers to be untalented?
Here we begin to get a glimmer as to the persona of the letter writer. It is someone who holds themselves above those of lesser mortals with whom they unfortunately must mingle during the course of their enlightened lives.