Free trade across borders was one of the first economic arguments I really found a firm footing on when I began to really dig in. Without thinking it through, it's easy to see the various reasons why people would be opposed to free trade. So I generally prefer a peaceable conversation with a dissenter over slamming them right off the bat. But this short communique between a doubting commenter and a faithful commenter really made me almost want to give up on economics altogether. The conversation was multi-faceted - I'll simply lift the relevant part:
Doubting: "You like to take thought experiments to their logical conclusions.... so what if some one invented a machine that produced everything the world needed."
Faithful: "If a machine produced everything the world needed - we could all go play croquet."
Doubting: "How would you pay for the croquet set or anything else for that matter? You wouldn't have a job."
Sometimes there just aren't enough words...