I don't know much about hiring. It's kind of fuzzy as to where we qualify as a protected class and how we quality with the ADA (disability act). I think that it is illegal to discrimination on the basis of disability where reasonable accommodation can be made, so im not sure how this works in regard to this job. But unless the job is directly related to speaking, such as news broadcaster, this sounds like illegal discrimination. And if they told you the reason is because of your speech then I would appreciate the honesty but it sounds like they're opening themselves up to liability. If you advertised to them that you stuttered (good on you) and then still called you back only to reject you later then this sounds they thought you might be a fit until some decision maker heard you speak and discriminated. But again, I dont know what job he/she applied for so I cant comment much. Op could check the laws in his country.