Porsche, I know what the definition of fetch is and I know that bosses give commands.

Yes, saying "please" before "fetch" would make it better received... but so would putting garnish and ketchup on a plate of horse manure.

It's not what you say. Its how you say it.

I'm sure there are plenty of settings where the word can be used with no harm.

@jeremiah first.. the reason you brought it up, is because of your friend's statement that addressed a boss saying "go fetch" someone.

the meaning does not change at all whether using go fetch for a dog or human.. in both cases it's a command.
a change in meaning would be to say, something like.. "that woman is fetching" meaning she's foine.

regardless if it's someone or something, it is still not a well received command in most settings

It's not an issue of definition. You don't go around calling happy people gay just for the sake of Webster's.

Tell people to "go fetch" in your daily dealings with them.. and see how they respond.