We so easily make fun of a stutter not in the most obvious ways, saying "Did I stutter" to reinforce what you said. Having a speech impediment is difficult, seen with my own cousin and friend. Growing up my cousin needed a speech therapist
Not being able to articulate properly for people to understand what she was trying to say, really affected her self esteem. She wasn't confident to speak, she still is a little. We make fun of people like her as if things aren't difficult enough as is
We take for granted the ability to speak and are very insensitive to those who struggle to. A stutter, lips, not being able to roll your "R's", etc..