Bang on.
Just because they wrote it, it doesn't mean they meant it.
It's a bit like the Dons on here, they have a room where they can let off - it doesn't mean they really think I'm a ***** ***** ********* *******
I would expect a work environment to be professional, especially if they are managers. They also say he's lazy, which is work-related. They should be discussing issues with him rather than insulting him behind his back which is nothing short of childish and unproductive.