The argument the more experienced African pros throw is that the cartridge really isn't legal, and that if it were an adequate cartridge, then it would be legal to use. Above that, if it were not only adequate, but extremely efficient, you would see them not only be legal, but you'd see pro hunters carrying them.
4570 will kill the game, the question has always really come to the immediate stopping power vs the bigger elephants, or cape buffalo.
The snobbish tone really comes because they have to dispute this issue almost every week on here, it gets annoying, gets old, gets beaten to death.
When it comes down to it, they have the experience, they hold the knowledge, they should be listened to.
As far as why the dig at levers, that argument I don't really know to much about, I've always read that they were a reliable repeater, and when face to face with a charging animal, I'd call that a big asset to have. I think I remember something about their excessive recoil...?? But the pros may be able to touch on their reasoning here.