In principle it doesn't bother me, but it does bother me from a guy who is only in his second season of playing, has already been committed one of the richest contracts in history, and who has accomplished nothing yet as a player. Don't get me wrong, I find Embiid's on court trash talk to be a bit refreshing and enjoyable to watch however the dude definitely needs to learn to be a good loser before he can become a good winner.
Talking about the instance with KG and RR, I think the circumstances were slightly different. That was already a championship team and that year was really their last chance at it. Much like Brady not making a huge effort to congratulate the Eagles after the SB loss.