they are representatives of the magazine, therefore they should behave in an appropriate manner and not tarnish the reputation of the magazine. especially on a public platform such a facebook.
This is the assumption you have made. By lets play on this assumption that you're are representatives of your employer and anything said personally or publicly should not tarnish the reputation of the employer.
Using this assumption and the ability to fire anyone who tarnishes the image of the employer (with the employer to to decide what is considered offensive to that employer) then you should agree that the following example then stands true and is completely "legal"/valid and we should accept it.
If you are a government employee the following is valid to be fired:
Any jokes about Zuma or the presidency is offensive to the presidency and tarnishes the government imagine.
Any whistle blowing, highlighting, or discussion about poor delivery service (tarnishes governments image)
Any attempt to air views or stances different from the government (brings the government into disrepute.)
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To extend this further, I shall show an example:
Hellen Zille, on her twitter feed, says that there should be a vote for no confidence in president Zuma.
This offends the presidency. Having a meeting mostly controlled by Zuma supporters they decide that tweeting such things has shown division in the Governments goals and embarrassed the presidency which ultimately is decided (by the "employers") this is offensive.
Zille is then fired.
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Example 2
I run my own business, we make cupcakes for victims of drunk drivers. One day I look on my employees facebook profile and see a picture of them at a braai, holding a beer.
Beer... that is unacceptable, it goes against the values of my company (I'm a real prick) and alcohol is not something we support at pink ponies cupcakes, especially since we are involved with drunk driving cases!
I will now fire this person for having a beer and misrepresenting my company!
Doesn't this look absurd?