The linked article presents a situation where the ten people you could save were chosen at random by a king. However, the people who you could save by giving to food aid charities are not random. They are specifically those who for some reason cannot produce enough to feed themselves. A few hundred years ago, feeding them would have prevented deaths in the short term, but caused an equal or greater number of deaths a generation later due to excess population. It also eliminates selection effects which would make future generations more productive. It may be possible to feed everyone today, but our moral instinct has had very little time to adjust to that fact, and it's still difficult to ensure our efforts aren't counterproductive. A lot of aid ends up being claimed by warlords and used against the people we want to help.