Drew McIntyre was on Wrestling Observer radio today with Bryan Alvarez and Dave Meltzer. McIntyre is best friends with Del Rio but declined to talk about the incident.
Meltzer said that the story on the Alberto Del Rio incident was that there were some people at catering and someone didn't clear off their plate and someone made a comment about "that's Del Rio's job." Del Rio later heard about it and confronted the person that made the comment. Del Rio asked for an apology and the guy just smirked at Del Rio. That's when Del Rio slapped him.
So, there is definitely another side to the story than what WWE is portraying.