I think there is one simple point you can make to rebut the second argument.

If both animals and plants have sentience, then won't it be better to consume one rather than consuming two? Just because plants have sentience and therefore vegans are not doing the right thing, doesn't justify eating meat is good.

And then, of course one can argue that perhaps vegans are consuming more plants than meat eaters, so perhaps the quantity balances out, but to that conclusion, it would just make both vegans and meat eaters equal I guess?

Btw I'm not a vegetarian though, lol.

I have a question. So one of the common questions people asks Christians is that "If God was perfect then why wasn't his creation perfect?" Then Christians would answer saying that because God made humans rational and gave them the free will, and free will can be used to do bad and good intentions, therefore good vs evil is not something of God's creation but of man's creation, and then they would also answer that because good and evil are what makes them each what they are, the comparison. But then here's my question: If God was omnipotent, meaning that he was capable of anything, everything, then shouldn't he have foresaw the outcomes of free will? Yet why doesn't he do anything about it?