Here is where I first heard the slang: Champion for Democracy? - Woodrow Wilson
Towards the end of the video, Neidell urges viewers to post their views about Wilson and says: "Please keep it civil!", in a seemingly cautioning, still friendly, manner.
I looked up its definition and as per Urban Dictionary, I concluded it's best suited for a heated discussion or a raw, not as friendly advice.
The question is: When should I use it? Does it reflect anger or intimidation? Could it be used in a friendly manner? And is it old-fashioned?