If your Tolstoy quote is accurate, it seems fairly sloppy reasoning to me. Animal protein is an essential component of nourishing billions of people. Calling sustenance “appetite” is a rhetorical flourish which undermines the argument.
I think what would be immoral is telling billions of people they can’t eat meat.
There are many ways one could prescribe humans should act to minimize their impact on the flora and fauna of our world. But at the same time, humans are entitled to a certain degree of leeway in this regard. Sustainably eating the plants and animals beneath us on the food chain is one of those areas.