I think Hussain’s argument is only surface level justifiable - If you take the context of the next game into account in justifying a punishment you end up with a perverse situation where eg joss butler can swear as long as the next game can be considered “important”.
Yeah, they shouldn't be taking the next game into account at all, I disagree with Nas there, but that celebration wasn't worthy of a demerit for me. He didn't get in Root's face, swear, bump him, any of that. Just celebrated and let out some frustration.
If you do Rabada there, you need to do every bowler who shouts while eyeballing the batsman as they run past.