Beaner is not an insult to Mexicans.
A popular mexican coffee chain is called Beaner Coffee.
I use the starbucks app to pre-order my daily Starbucks and you can put whatever name you want to be called on the app, including Beaner, slut , cumguzzler, the N word , etc.
There used to be a fat Mexican immigrant here that used the handle Beaner. Another fat Mexican immigrant here was called Escorpio and he was racist as fuck.