Do grown adults actually make fun of people's stutters when they are fully aware of the condition?

Do grown adults actually make fun of people's stutters when they are fully aware of the condition? Obviously I've heard a lot about kids making fun of stutters because kids are just cruel, but the only times I really hear of adults being rude about someone's stutter is when they don't fully understand what stuttering is or that the person they are making fun of has a stutter. I've heard a lot about people being mocked, but than once they tell the person "I have a stutter" the person usually apologizes. In Your experience, do you think people who make fun of stutters are just ignorant about the condition? I can't imagine a grown adult making fun of someone's stutter if they are aware of the condition unless they are a complete psychopath.