Nalby has always had a temper unfortunately, and although he didn't mean it in the heat of the moment it was right for him to have to default the match. He seriously injured someone and no matter what the crowd thought of it those are the rules to be enforced. As much of a disappointment it was that the match had to end, it would have reflected badly on the tournament if it continued. On the other hand the crowd was being very unforgiving about what they wanted - they wanted the match to continue but that would have been a bad atmosphere afterwards anyway with Nalbandian probably being booed every point. And then to make things worse Nalbandian made that rant about the ATP with a pretty weak apology mixed in there; just a completely unthinking decision, much as he had made to kick the advertisement board mere minutes before.
Felt sorry for Cilic having to win this way because he was starting to turn the match around before the event, but he gave a very temperate winner's speech to appease a pretty intransigent crowd.