I get criticized by my family for having a large vocabulary all the time, and we're Irish blue-collar types. My mother says she feels like I'm talking down to her when I use "big fancy words". I pointed out to her that, by assuming that she knows the words I'm using, I'm actually doing the exact ****ing opposite. If I wanted to talk down to her, I'd use small words. I'd assume she didn't know the big ones. Ultimately, it's her own insecurity that she's projecting on to me by creating artificial motivations for my vocabulary choices. She feels inferior for not knowing the word. She doesn't like feeling like that, so she blames me for her own feelings because, in her mind, I "caused" them. It's the same thing with people who criticize you for speaking how you do. They're insecure about their own speech, and you remind them of their insecurities, so it's "your fault".
Instead of smartening themselves up (which takes self-analysis and effort), they want you to dumb yourself down. I say **** that noise.