I'm so sorry that happened to you, I've had this happen more times than I can count on 1 hand both professionally and personal bullying. Did you tell them you stutter? I tell them, and I also let them know "if I stutter it's not because I don't know the answer or that I'm nervous, I'm excited to be here, I'm just one of the people in the world who sometimes stutters." Something along thise lines, usually with an amused smile which helps facilitate the acceptance reaction im aiming to draw out of the person. 95% of the time, at least professionally, people are cool and explaining it upfront I think makes all the difference. Without telling, I feel like people tend to think that stuttering indicates extreme nervousness or lying. I believe more awareness now helps, as well as we may be seen as disabled and people don't want to be sued for not accommodating. Regardless if this is a disability or not, you know some people think that so it is what it is. You should report the interviewer to the company. I've actually reported an interviewer and had good results from it and extensive apologies received. As far as does it getter better mechanically and coping. For me, good news, I'm a 30F and yes my stutter and blocks are more in the mild category now, as in many days i only stutter or block a few times a day, previously I was worse my whole life. It also helps that with age you become far more comfortable in your own skin, I noticed that shift in my late 20s. I too had an interview the other day for a scholarship for my career change, I was fluent 90% the whole time and surprised myself. I'm talking more in daily interactions (previously I let my husband speak for me for years) and surprisingly I'm just far more fluent these days. Yes, im still sadly having to do the mental work and speech strategies to remain fluent. Keep in mind that brain continues to develop and change as late as the mid 20s. I'm not sure if something changed positively in my brain mechanically or if my greater comfort in life due to age has psychologically helped. But that's just my experience, I do know there are some people who don't necessarily experience stutter reduction mechanically but they become better psychologically by acceptance and therapy. Just don't give up, you are so young I wish I got started self improving at 23, I didn't do much in my life a large part being due to stutter, don't give up you don't want to put things off like i did! You got this :)