Few things to point out here. The rules from my understanding permit using natural methods to maintain or enhance the state of the ball but not hasten it's degradation. And I think that's why there's much more furore over this incident that the previous ones.
Most of the previous ones involved using gum/lollies to enhance the shiny side of the ball, while this (along with the infamous Faf zipper), was deliberately used to degrade the rough side of the ball. I can confirm have played as a bowler that degradation of the rough side, especially any movement of the seam in particular is what hastens the onset of reverse swing. The fact that this action was so deliberately planned out during lunch and rubber stamped by the 'leadership team', paints the Aussies in the worst possible light.
Yes, Pakistan have done it in the past as have other teams; however, there's no doubt in my eyes that it has reduced a lot in the present day thanks to cameras in particular. It's very hard to pull this crap anymore.
Secondly, the Aussies have shown themselves up as the worst hypocrites in the world game. They push the line, headbut it, have their innocent coach Lehmann ask the crowd to sledge Broad bad enough to make him cry and go home, be pulled up for cheating in the past and push it away as a one-time thing (2008 Sydney, Brainfade).etc. Their record is abysmal and easily the world of any major cricketing nation and they have the gall to cry like babies when the shoe is on the other foot.
The fact that this happened the day after they made an official complaint about the crowd for disgraceful behaviour is the most beautiful symmetry I've seen. Sadly, they wont be in Pakistan anytime soon, but I hope Indian crowds give them the absolute worst.
