Will Smith is an absolute asshole. He laughed at first then when he realized Jada wasn't impressed he flipped in a second. He's old enough to be able to control his temper and to know that his behaviour was ridiculous and unacceptable. His pride was injured because he didn't want to look bad for laughing while she rolled her eyes at them both. Now he's fucked everything.
The joke was badly received and would have been quickly forgotten or Chris Rock would have been the one who looked like the dick. Now it will be immortalised in that clip as people want know the joke that prompted his response. She'll be asked about it for years to come (as will he)
Smith also won his first Oscar but now searching for Will Smith Oscar is always going to show him slapping Chris Rock. He spent his speech grovelling, yet no apology to Rock. Also his "love makes you do crazy things" stance is a textbook abusive husband line. Not exactly a great look.
The joke was in poor taste but Smiths behaviour was much worse. The academy won't give a shit though. If they did he wouldn't have been allowed to just sit back down, receive this award and party the night away.
Unsurprising since the Academy gave an Oscar to Roman Polanski who was convicted of the rape of a 13 year old when he was 43. This was back in the late 70s. He fled the US when prison looked likely and has never returned. The scumbag has since been given noms and honours for his movies (he won an Oscar in 2003) rather than being forced into obscurity or better still jail where he belongs.