Good reason for Elon not to pick fights with Jeff of Amazon.
A few thoughts:
1) The rivalry and apparent animosity between Jeff Bezos and Elon predates by many years the recent tweets from Elon about Amazon. I don't know who started it, but one might say Jeff "picked a fight" with Tesla when he ordered 100k electric vans from Rivian (a startup with no released products yet), instead of the leader in electric vehicles.
2) The van market is much bigger than just Amazon, so the "fight" seems unlikely to hurt Tesla.
3) If you mean Elon shouldn't criticize Amazon at all, I disagree, partly because of #2 and partly because Elon's principled candor endears him to many people.
4) Amazon has a history of squeezing every possible penny out of operation costs, so if Tesla produces a significantly better van than Rivian (which seems likely), Jeff might buy them for business reasons despite his feelings about Elon.
In short, I don't think Elon's Amazon tweets were foolish emotional outbursts, of which he is often accused.