Condescending means they feel like you're beneath them. I can see how some people might see a stutter that way, and might do it in a shitty way, but I feel like the majority of people do it with the idea that they are trying to be helpful and friendly, like "here I see you're struggling with this word so I'll make it easy for us both and just say it so you don't have to struggle any further." I agree that endless teaching moments are not something that anyone looks forward to. I just feel differently about it, and try to give people the benefit of the doubt. I don't think anyone thinks they're above me because they offer unwanted assistance, that's all.