One stereotype of Americans I've often heard from foreigners is that a lot of us go to other countries and expect everybody to speak and understand english.
I think it's about the same with vocabulary ranges within the same language. No sense expecting people to understand you when they don't.
Big words don't mean you're smart, or even skilled with language. Take a look at some really good literature, poetry especially, and see how much they use fancy words hardly anybody understands.
Like E.B. White and Strunk said in the classic, The Elements of Style, "Never use a twenty dollar word when there's a twenty five center handy."
Okay, I gotta admit, I share your vice. It is nice running language directly from the brain to the mouth without censorship. I just don't do it all the time. Depends on who I'm talking to.
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They murdered boys in Mississippi. They shot Medgar in the back.
Did you say that wasn't proper? Did you march out on the track?
You were quiet, just like mice. And now you say that we're not nice.
Well thank you buddy for your advice...
-Malvina