In the case of Gallipoli, I think it's somewhat justified - the campaign was a disaster. But that was hardly unique in British campaigns of the early to mid-war.
Breaker Morant, on the other hand, was a war criminal - I have some sympathy for Handcock and Witton who were probably not educated enough to understand they'd been given an order contrary to the rules of war - but Morant was. He killed out of revenge, pure and simple and while that is understandable, it's not acceptable in an officer. Should he have been shot? Probably not, but the fault for that lies with the Australian government - Australia had just become an independent nation at that stage, and it failed to make any representation on his behalf. If it had, he and Handcock would have probably been treated as British officers had in similar circumstances - cashiered and sent home.