@Celticfox,
At the risk of sounding condescending, I'm tempted to assume that you have some kind of kindness/nurturing instinct to respect or protect the people that you care about rather than, say for example, attempting to maim them and waging war on their territories.
And I admit that if you properly backstab a 12-year old, you can expect to face plenty of profanity and tears.
Might I suggest setting up a game with some of the older/mature players? For example I'll point out this game:
gameID=128876 Where I got stabbed probably three or four times in rapid succession, and then spent most of the game cowering in a corner (of Turkey).
And I was laughing most of the time because I'm tough and find backstabbing hilarious.
Yeah, try gaming with some older folks who have a sense of humor about this sort of stuff, and maybe you'll feel a bit more comfortable stabbing, stabbing and stabbing away!