Do you remember the Australian was running so his weight was provided mostly to the back leg?
So? You don't know what you are going to hit.
A yellow card should have done very well.
That may be your opinion but the FIFA instructions are clear. Personally I would favor being able to send of people on a personal basis like a forced subsitute so the match isn't influenced that much.
Just for some cases, even during the World Cup
Yes. But that doesn't mean this call was wrong but that the others were incorrect or not in agreement with the rules and the instructions. Like you said, sometimes the referee must have a feel for the match and not influence the outcome with a red card.
Do you have a proof for that?
Proof? I assume you did see the tackle. He hit his teammate with his right leg while he initiated the tackle with his left leg. That makes two legs.
Materazzi did not hit the Australian player with full force. He moved the legs forward but stopped before it hit the 2 players.
Stopped? How can you stop in the middle of a tackle. He jumped forward. The moment he does that he was no way to hold back. And yes, he didn't hit the australian with the studs of his shoe but that is irrelevant. He might have. The intention is what is judged. The tackle was reckless and potentional able to injury. The ref doesn't need a doctor the examine bruises, broken bones, damaged muscles and tendons to come to a judgement.
Clearly this example is very clear. Why do you have problems with it? I don't see much room to challenge the referee's descision.
Evenmore so since this was not the biggest mistake in this particular match.