I think that may be the reason it bothers me so much is because you're right, it usually is the same person that does the 'just slow down' comment when I'm struggling. And it's like a slight to me because I know it's different, and I don't like someone looking at me as if I could fix it if I just tried. If just slowing down made me fluent, I'd do it. But that's not the case and I don't like someone telling me how I could be fixed when they truly don't understand the struggle. I know it's not a mean thing on their part, and I don't hold it against them personally, but it can be a frustration.