There's nothing wrong with it if the animal is treated well
Welfare standards vary, and some genuinely reduce suffering. The contested step is letting the word 'humane' stand in for a justification of killing that isn't necessary.
What makes eating animals wrong, if anything does, is the suffering involved, and that suffering is not inevitable: effective stunning renders an animal unconscious before it dies, and good transport and housing mean it can live and die without the fear and pain critics describe. If an animal has a decent life and a death it never experiences, then killing it humanely and eating it is not cruel, and refusing all animal products goes beyond what compassion requires.
Effective stunning, lower stocking densities and shorter transport do reduce suffering, and the difference between a well-run abattoir and a poorly run one is real. It is worth conceding that plainly, because the argument does not turn on it.
What the term does is shift the question. 'Humane' originally means showing compassion; applied to a method, it means 'causing less suffering than the alternatives'. Those are different claims, and the argument works by treating the second as though it established the first. Whether a less painful death is a justified death is exactly what remains to be shown, and the word quietly settles it. Compliance also varies in practice: stunning failure rates are non-trivial even in regulated facilities.
- Humane slaughter exists
- I only buy free-range or organic
- It's okay to farm them as long as we kill them humanely
- They had a good life and a quick death
- We gave animals a good life before slaughter
Different wording, same argument. The response above answers all of them.
Defining a term so that the conclusion is built into the definition, winning the argument by stipulation rather than evidence.
How it applies here: Builds the conclusion into the word. Once slaughter conducted to standard is defined as humane, there is nothing left to evaluate: the ethical question has been settled by stipulation.
Using a single word in two different senses within one argument, so that a conclusion appears to follow when it does not.
How it applies here: 'Humane' shifts between 'causing less suffering than another method' and 'morally acceptable'. The first is a measurable comparison; the second is the conclusion being argued for.