I disagree with this too. It's a natural, instant reaction here. I think it would be worse if the guy was stewing it for the rest of the period then blowing up in the locker room. At least this one is just pure instant frustration.
Besides, we see coaches yell at players all the time, teammates yelling at eachother during the game isn't all that uncommon either. And yes, I'm going to use another MacKinnon example (and yes, he has more clout than Georgiev), remember the exchange he and Bednar had years ago?
In normal work, showing these type of disagreements in front of customers would be very stupid, I agree. But it's sports, what matters is winning. Thus, it doesn't really matter all that much what we think of the situation as long as it's fine in the locker room. And like I said, having a snap reaction is not as bad as blasting someone behind the scenes when there is time. At least that's my opinion.