Avoiding suffering isn't the highest good
It doesn't need to be. The case against eating animals doesn't say suffering is the only thing that matters, just that causing it without need is wrong. Whatever you think the highest good is, a farmed animal's suffering doesn't serve it.
A life organised around avoiding suffering is a thin one. Meaning, courage, love and achievement often involve pain, and the best human lives aren't the most comfortable ones. If suffering isn't the worst thing and comfort isn't the best, then 'it causes suffering' can't settle a moral question on its own. It has to be weighed against other goods, and that weighing is more complicated than vegans allow.
Almost no one thinks avoiding suffering is the highest good, including most vegans. The claim being defended is narrower. If you can get what you want without making another creature suffer, you should. That fits nearly any account of what matters most: meaning, flourishing, virtue, love, duty to God. You can hold that a meaningful life is worth some pain and still hold that hurting others for no good reason is wrong. The two don't conflict.
So the real question is what higher good the suffering of a farmed animal serves. Meaning is the usual candidate, and it is a serious one. People do find meaning in hardship they choose or endure: training, childbirth, grief, caring for the sick. But that meaning belongs to the person who bears the suffering. A pig or a chicken gets no meaning from being bred, confined and killed. Whatever meaning exists sits with the person eating, and a meal can be just as meaningful without the animal in it.
This holds across farming systems. Better welfare reduces how much an animal suffers. It doesn't create a purpose for the suffering that remains, or for killing a healthy animal a fraction of the way into its life. Transport and slaughter happen on the best farms too.
If avoiding suffering isn't the highest good, it still counts for something. To outweigh it you need a good on the other side. For most people choosing dinner, that good is taste, and taste is available without it.
Replacing someone's actual position with a weaker, distorted version, then refuting that instead. The original argument is left untouched.
How it applies here: The vegan asked whether you ought to do something without causing suffering when you can. The reply treats this as a claim that avoiding suffering is the supreme value, then rejects that larger claim. The actual question, whether unnecessary suffering should be avoided, goes unanswered.