It takes a looooot to make me actually rage at a teammate. 90% of the time I either know we're all sucking or else direct my anger at the enemy team. To get me to actually get angry at you as my teammate you basically have to:
a.)start raging at me first, calling me a "noob" for getting first blooded, acting like the situation we're in is my fault when everyone's making mistakes, complaining about bad support from the only support, etc
b.) or make a really really really dumb move and have it work out exactly like I predicted. I mean really unfathomably dumb. Not just "pick a hero I think isn't optimal dumb", but "grab Weaver as a third carry, do nothing with him and die 8 times in 30 minutes" dumb. See the entire enemy team walk into the Rosh pit and then walk in alone and die when we're all across the map and complain that we're not there dumb
The second category, incidentally, has happened like three times to my recollection. The bar is really high.