Those bans were no doubt harsh, but context matters.
Most of the Australian public was fed up with the behaviour of that particular side and particularly Warner. Sandpaper was just a sympton of the total lack of decorum and respect for the game that side had. The ban was reactionary and over the top, particularly with the benefit of hindsight, but there was more to it than just what happened at Cape Town.
One of cricket’s finest ever exponents of reverse swing bowling, Wasim Akram, has raised doubts that Pat Cummins did not not know sandpaper was being used on the ball in South Africa.