I think England are sore about this because they are ultimately just too casual in their cricket to ground their bats. It seems like they have a pally relationship with the Australians up to a point and trust them not to do something considered unsportsmanlike, but ultimately, Australia are more fixated on winning, hence the dismissal and the manner of it.
I honestly don't have a problem with the dismissal. It's within the rules and it is the Ashes. Australia want to win and England should be the same.
I don't expect England to go looking for a mankad-style dismissal or uphold one should it be effected, but why should they not expect it from Australia? They may seem like their 'mates', but they desperately want to win and that's a way they can get you out. By the laws of the game it's legal and England should not be holding up Australia to this 'gentleman-style' level that they are doing.
Just ground your bat and be switched on. It's professional cricket.