Is it proper to speak foul words in public to your subordinates?

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Today at my job., the project management consultant or PMC roamed around the site area. He saw that theres a man working down the tanks grinding the walls..as he was walking he noticed dust arising..He was so furious and he shouted at the ham radio to the laborer,"hey you..stop grinding!...you *$!?(* id better send you off!..or you want i'll shoot you! ---whew, from what ive heard from him at the radio, that makes me wonder why he just did'nt told the project engineer assigned or the contractors project manager.I believe what he did is very unethical and he himself stoop down to the level of the laborer already. I just wanted him to learn his lesson and not to treat laborers like that,,besides he is a consultant and he should have acted as professional.,what do you think guys?