He didn't clench his fist. Before, during, and after the swing, you can see his hand ISN'T clenched. It's certainly not fully open like a slap, but it is far from closed.
He intended, at the very least, to get Crowder off of him. After all, Crowder just committed 3 fouls that the refs ignored.
Yes, he swung hard. You usually do when you're clearing someone out that just shoved you 10 feet. Go watch the play again.
The real question is are you from Beantown or the windy city? Either way you're full of hot air.