I know of someone who was fired for using the word "ghetto". Used it in the context of a very poor, mostly minority neighborhood. My understanding of the situation is that she was at lunch, off work premises, but overheard using the word. She was promptly fired.
Iowa is an at-will state, so you can be fired at any time for any reason, but she was able to get unemployment - the state did not consider it to be just cause to deny unemployment.
This particular workplace is very sensitive about being politically correct, but took it a bit too far on this one IMO. Had she been on the clock or talking with a client, OK. But at lunch offsite? To go straight to firing without offering a class of some kind was a bit harsh.