i think the whole "video games promote violence thing" is a load of crap.
i play shooters, all the people that i know who play shooters(even the ones who are gun nuts) are docile people. games like CoD, L4D, TF2, GoW, ETC., let you do things you cant in real life. you get to experience a simulation of war(CoD,Battlefield,GoW) survival(L4D,Dead Rising, Dead Space, Killing Floor ETC.) or just plain killing others with a sort of humor attached to it.(TF2). yes, some people are agressive, and SURPRISE! some of them play video games. and, with all respect to you and the examples you chose, i bielive that they are wrong for your argument. your Tekken example: i used to play Street fighter at an arcade with buddies and random people there. and, like your example, things would get heated up, to the point where we DID end up in blows.now is that because of the video game? or our competitive nature? if we had been paintballing, playing football(the real kind, not handegg =P), or basketball, the outcome would have probably been the same. competitive people will be competitive.
as far as your second example, i turn to this:
now im not calling anyone a retard with this, but what i am trying to say is that it is not the persons fault(child or adult)for wanting to replicate something they saw, but in the case of the child, proper guidance should be provided to teach them that not everything that they see is real, nor should they try it.
TLDR?
1. people will be competititive, no matter what the activity
2. kids will be idiots that want to mimic every cool thing they see on tv/movies/games. but its up to the parents to teach them better.