Vegan reply to: "I eat meat, because if I don't eat and kill animals, they will have a worse life in the wild."

Lauren,
You wrote: "I have been inside a few abattoirs in Australia and I have no problem in the way that they operate,"
You don't have a problem, but it is not about you, it is about the animals.
Do you really believe that they want to be killed by humans? Do you believe it is morally justified to inflict unnecessary harm and unnecessary death on sentient beings for pleasure/convenience/habit or tradition.

You wrote: "The fact is that these animals would be having a far less peaceful life and death of they were out in the wild which is exactly where they would be if they were not grown for food."
This is an assumption. And you are assuming the animals rather be confined and domesticated, that cows and calves prefer being separated from each other within a week of the birth of the calf, and then finally murdered by humans.
And then you try to defend this by saying that some other animals would inflict even worse suffering and death upon these harmless sentient beings. Lets assume it was true.

Lets apply your reasoning to a human context.
A person knows that another person will be tortured and murdered by another human. In order to prevent this he/she goes to the person that she knows is a victim of a planned murder, and kills him/her in a less painless way.
Then he/she try to morally justify the murder by saying that he/she prevented more cruelty and harm.

Do you think that this is morally justified?
I find it incredible how many non-vegans believe in nonsensical "justifications" to inflict unnecessary harm and unnecessary death on sentient beings for "palate pleasure"/convenience/habit or tradition.

The need to come up with such excuses shows that they on a deep level don't believe it is morally justified to consume animal foods.
I opted out from animal exploitaiton last autumn and went vegan. You can do the same. It only requires that you care about the animals.