There should be an imaginary line/barrier on the field of play/dugout/whatever you want to call it. Both sides should be able to yell whatever they want short of the N-word but nothing physical should ever cross the barriers.
So in the terms of the pathetic proposal, that guy is in the wrong because he crossed the barrier and should have been shot by snipers before he even got down on one knee.
In Rendon's case, which is far more understandable IMO, he crossed the barrier and is in the wrong and should probably receive a 10k fine and 1 game suspension.