This reminds me of a rather frightening incident I heard of, On one our local quake servers there were 3 clans (i was in and eventually led one of them) however our clan kinda sucked so it was mainly the other 2, but one day these 2 guys REALLY got into it online and exchanged the usual "kill you" remarks. However some days later i headr that some guy that had his Quake name on the back of his truck has his tires slashed and his car was keyed pretty bad too. I dunno if it was the same guy and whatnot but its food for thought.
By far the scariest argument i have ever seen was at a gun range, nothing is more horrifying than 2 redfaced spitting screaming rednecks each with a 3rd world country arsanal at arms length.