There are two issues to hash out, the moral issue and the sustainability issue.
The moral question is a matter of opinion and perspective (though it's linked to the sustainability question). I think it can be interesting to have a discussion of the morality of eating animals. You assume quite a lot about my motives, but from here it looks more like you are the one who have made up your mind, and aren't worth engaging ;).
I'm more interested in the sustainability question though. You seem to be mixing up several issues and not really addressing the question. The question of feeding the whole planet is different from the question of how to feed myself (note that I use the pronoun "I" and not "We"). I do not feel obliged to make up for unsustainable practices of other people, if my own practices are net positive for the planet; I am curious to hear vegan thought on that perspective. The question of who eats meat is not binary - not all seven billion people should eat meat (much of India doesn't), and your suggestion that "one person being allowed to hunt" is so childish and really unserious.
Point is, it sounds to me more like you are making a blanket assertion about sustainability which isn't really true. Many things aren't sustainable; e.g. the amount of hydrocarbons that you as an individual are using every day just by living, is not sustainable. Are you quitting though? I'm willing to bet that a great many small farmers are doing much better than you are with regards to sustainable living, but you're probably so careless with the details of how you live that you don't even know for sure.