"The continual use of slang expressions is an evidence of mental laziness, and I will not hire a man who depends upon slang to express his meaning. It is a substitute for exact thinking." I found this to be an unusual warning. Is "proper speech" really just a proxy for class in that time period? I'm now very curious about 1920s slang, especially its frequency of use in business settings.
I read 'slang' as buzzwords, and I think that statement is equally valid today.
Linguistics are an interesting thing, especially with geeks. Often, their analytical minds concoct elaborate sentences, which, like algorithms, are abstractions over many little things. I prefer the plain talker, the man who has seen the cathedral of long sentences and has realized only the priests understand him.