I agree the situations are different.
My points are simple ones.
1) Belichick would have benched Gronk, and we would have been more likely to lose the game.
2) Kelce's actions were clearly wrong. The reaction of the players, QB and coach were to understand his actions and to be more focused after the event.
===================
With regard to Welker, Butler and so many others, Belichick had his system. It worked for 20 years, even though it seems that it could have worked better in these instances and in some others where starters were didn't start because of minor offenses. So, with Belichick, obviously the good of his system of discipline outweighed the bad and think it unreasonable to look back and criticize.
We still have awhile to continue to criticize Belichick's 2nd stint, the rebuilding one over the last 4 years. And, then, we need to even move on from that, only remembering the greatest franchise, coach and QB, all time over the 20 years.
==============
AN ASIDE
Reid's system of treating players works for him. He does indeed treat Mahomes and Kelce differently, and allows confrontations, although obviously this was extreme. I'm sure that Reid, Mahomes and Kelce will have a hearty laugh about this. And I don't think anything will change as they challenge NFL history with their potential threepeat.