This is the oldest example that I know of where the the quality of a person’s language is used to single them out. And as strange and bloody as this passage from the Old Testament is, the use of language as an identifier, or Shibboleth, is still very much with us. Consider what would happen to a candidate in a job interview who, in deadly earnest, said, “Lemme axe you a question.” Unless the interview is for fry cook at McDonald’s, this non-standard use of language would put a serious dent in the interviewee’s chances. It’s not worth trying to argue with this linguistic prejudice. It exists and we all have to deal with it. We are judged by the way we speak and write. Sadly, there ain’t much rational about these kinds of judgements. You know exactly what I meant by that last sentence, but, chances are, you had an emotional reaction to my use of the word “ain’t”. To write well requires a sensitivity to these nuances of language. Ya’ll know that. In fact, most of us manage our spoken diction very well. We don’t swear in church. We don’t curse around small children. I favor a kinder, gentler, more forgiving, New Testament approach to language. I appreciate people who are direct and clear in all of their communications, and try very hard to pay more attention to the substance of any message than the wrapping. To me, that’s the only sane way to look at business communications. In a more perfect world, that’s how I think things would be. People who spoke and wrote correctly, yet had nothing to say would be ridiculed. But the world is not like that. In fact, I’m not sure people have changed much since Biblical times. Trip up on one of these Shibboleth terms and you probably won’t get killed. But your career might.Judges 12:6 Then said they unto him, Say now Shibboleth: and he said Sibboleth: for he could not frame to pronounce [it] right. Then they took him, and slew him at the passages of Jordan: and there fell at that time of the Ephraimites forty and two thousand.
The reason they used that word is that non-native speakers (i.e., foreign spies — generally not welcome regardless of socio-economic status) couldn’t pronounce it.
The rest of your conclusion is spot on, and it works both ways. I grew up surrounded by well-educated people who spoke “standard English”. You can imagine how well I fit in at some summer jobs.