If you buy my product but dont read the instructions, thats not your fault, its mine.
If you read a blog post and misinterpret what I said, thats my choice, not your error.
If you attend my presentation and youre bored, thats my failure.
If you are a student in my class and you dont learn what Im teaching, Ive let you down.
Its really easy to insist that people read the frigging manual. Its really easy to blame the user/student/prospect/customer for not trying hard, for being too stupid to get it or for not caring enough to pay attention. Sometimes (often) that might even be a valid complaint. But its not helpful.
Whats helpful is to realize that you have a choice when you communicate. You can design your products to be easy to use. You can write so your audience hears you. You can present in a place and in a way that guarantees that the people you want to listen will hear you. Most of all, you get to choose who will understand (and who wont).