Not sure why anyone is surprised, this is typical behavior from Smith. Although the media has done a pretty good job protecting him and his family.
He has struck fans, and a reporter in the past, however those are quickly forgotten seeing how they were not on live primetime TV.
Let's not forget about the dust up between he and Alfonso Ribeiro (Carlton Banks) from the days of The Fresh Prince of Belaire. But that incident backed fire on Will, Alfonso whipped his butt.
I will say regarding this incident,
@Inner Space is probably more correct, it all seemed a little bit scripted. A poor attempt to bring Will back into the limelight so to speak. After all, how many even seen the movie, or if they did, think he deserved the nomination and win?
Then you factor in nobody really watches the Oscars anymore. It's all just a little to convenient seeking attention.