Just take it as part of entertainment since both guys want to prove something and maybe they don't like each other since they see their selves as close rivals. And its also fun to watch those guys trash talking to each other since this heat up the game and we can see a great duel between them. If they reach up to playoffs then Suns and Mavs will face up then this is exciting game to watch since for sure we can see more heated arguments between those guys.
Likely that's it, people love some altercations. For me, even with the addition of Durant, Mavs has still a chance to beat them if both Luka and Kyrie are healthy and I hope they end up taking the first round in the playoffs or even second round.
Not new. Booker did the same thing before against Luka, it even went further that even the coaches are getting involved especially, Coach Monty.
Remember, they met last year in the 2nd round of the playoffs where the Mavs won so this rivalry is still there, just sleeping and maybe starting to wake up again as the playoffs gets near.
I think not bad for the Pelicans too since the rivalry was still there regarding the dunk with 1 second left in the clock, they got a good match if only Zion is there but this guy is prone to injuries.