I usually just smile (in a fuck you sort of way) and continue the conversation. I'm 24, so the people I converse with are mostly adults. If a fully grown adult resorts to mockery, I'm more embarrassed for them than myself. Especially if they do it in front of my friends who know I stutter, because now they have just made an ass of themselves in front of a group of people. I'm not gonna lie, it still stings and brings back memories of being mocked as a kid, but as an adult, what is more embarassing: stuttering or being the one mocking a stutterer?