OK - it looks to me like Will Smith was reluctant to do/say anything, but was spurred on (by the evil side-eye) by his adulterous and controlling wife (who is herself accused of being a sexual predator, as has been widely reported) to do something.
He strolled up, thinking it through and decided that he couldn't back out and knew a punch, from a trained fighter (yes, he did a lot of fight training for various roles) would be serious assault. a half-hearted slap and some classless shouting was what he settled on.
Someone with a better thought process may have handled it differently - like Denzel or similar - but he didn't.
Now there have to be consequences. It took away from the awards he and everyone else received. It dirtied the show with violence (mild or not) and it is now the talk of the world.
I think perhaps he should keep his best actor gong, but be publicly censured in some form by the Academy. Maybe a suspension from the membership?