It sounds like your comment to him bothered you since you say it happened 4 months ago. Most people who stutter want the same patience, respect and present listening as anyone else. For me personally, as an older woman who stutters, it has never helped when anyone even with the best intentions, offers advice like “slow down, take a breath, think before you speak, just breathe!” If those really worked don’t you think all stutterers would know that and use those tools. I find it’s always best to just listen, be patient, make eye contact and give me as long as I need to convey my thought. I would do the same for you, whether you stutter or not. Being present with an individual means you know ( or should know) how best to interact. Part of the reason stuttering is still so wildly understood is (imho) that we are still seeing stuttering as mostly a defect rather than just a difference.