The first quote is very true indeed. I think it’s because our affliction is a behavior which even non-stutterers demonstrate, just far less often. Everyone (non-stutterers) stutters on occasion, so other people might be quick to assume the person they make fun of (saying things like “c’mon, spit it out!”) is a non-stutterer who is having a fleeting difficulty with their fluency, instead of realizing they are speaking to a real stutterer who has dealt with it their whole life. This, of course, only explains why some people make fun, but not all.