Unless you can disprove GP's three arguments, we're talking about a trade-off. Trade-offs should not solved by rhetorics and ideology but by a careful cost-benefit analysis.
The parent's argument is exactly the same if we change "giving people food" to "giving people who have food that isn't suitable for them food that's more suitable for them".
Maybe you think that the parent's argument is flawed because you think that all people have the same basic educational needs. That's what TFA is arguing is not true, but maybe it's wrong; you could make that case. But quibbling over the exact formulation of an analogy is not the kind of concrete thinking that you're asking for.
Determining the value in integrating "gifted" kids with "non-gifted" kids is in effect the same argument that is held with regard to determining the affect that charter schools have on our school system, simply change the modifier from gifted/non-gifted to interested/uninterested in school and we are having the same debate.
There are pros and cons to both models and people have to admit to both sides of it, otherwise they are being disingenuous with their analysis.
Presumably even in my analogy the people not given food had some food, since they were merely weak and not starved to death.
But that ignores my argument anyway! My point is that you should do what you can do, even if it's imperfect. The food analogy was to show that the argument 'don't help some people because it's unfair to the people you don't help' is extremely stupid.
That's a moral argument, and my reply was a moral argument.