I’ve had people assume stuttering was like a drunk person slurring their speech in that it was caused by our actions (like we do something to cause it). I’ve also had people tell me “just spit the words out” and of course there’s the people that assume you’re lying or nervous around them. I can see why they’d think those things, speech for normal people is kind of an automatic thing, they think what to say and the words just flow out with ease 99.99% of the time. The only times they have issues are when things like I stated above are happening to them. I totally see your friends point, even though they where trying to be supportive they were kind of shaming you in a way, even if they didn’t mean to. I think the way I would offer a rebuttal if I was interacting with your friend is to say that a person that stutters has to expend lots of extra energy just to talk. We have to manage our words, we have to constantly focus on our interactions, even the ones that are mundane and run of the mill. So if a stutterer doesn’t want to do something, even if other stutterers have done it in the past, it’s not because we are letting the stutter win and guide our live’s, it’s because we just don’t want to expend the energy, we have better things to spend it on. It sounds like your friend is willing to learn and understand what you’re going through, which is always a good thing. Be patient and eventually they will understand.