For the entirety of my playtime (since beta), I have literally never seen one of these that wasn't warranted. Remember that OP always has incentive to paint themselves in the best possible light.
According to the Red in this thread, this was the nicest chat log in the report, and it wasn't that nice. Can you imagine being in that match? Worse still, could you imagine being the target of that? He tilted his own team (and likely lost) for no other reason than he's an infant.
Now multiply just this chat across a handful of games and ask how many people's match (and sometimes night if they got tilted enough to quit) he single-handedly ruined. So was it that bad? No, probably not in isolation (depending on how you personally view the insult "retard"), but given that he's probably not even that polite, and he's almost certainly does this on the regular, yeah... 14 days and good riddance.