I am actually starting to get what he is looking for here. Basically, he doesn't want a character to have to give up their other capabilities to be defined as a natural born leader - perhaps in one party, Gandalf is the inspirational glue that holds everyone together, while in another it is Aragorn, and in yet another it is Frodo. Whether Wizard, Ranger, Fighter, Rogue, whatever - having that role of 'inspirational heart of the party' doesn't need to be tied to class.
Which I can understand. But at the same time... I sorta feel like you could make that same argument for Fighter, or Bard, or any number of other capabilities. Once you go down that road, you truly are looking at designing an entirely class-less system.
As it is, D&D somewhat assumes that if you really want to have those exceptional abilities, you need to represent it within the character's stats. In 4E, it presents the Warlord as one way of doing so - the most prominent way. Basically, they decided that 'inspirational leader of men' was a valid enough fantasy archetype to merit its own class. I don't think there is anything wrong with them doing so, or unrealistic about that (any more than the concept of any class.)
Could they have pursued a different approach, and made it some sort of template option (as seems to be showing up with Dark Sun themes?) Sure, probably.
But as has been noted - there are other options. As mentioned, every has this to some extent via Heal and Second Wind. Investing in Diplomacy, hunting down the right utility and skill powers, multiclassing - all these can help a character gain some of those talents.
Without that - you might be a naturally charismatic fellow, but you just haven't mastered the art of truly inspirational speeches, because you've spent more time learning to swing your sword and other tricks. Haven't we seen things like this before, as well? Rogues being the only ones able to find magic traps, for example - even a bard who is incredibly skilled with traps, natural dextrous and perceptive and such, can't ever be as good with traps as someone with the 'trapfinding' class feature?
In this case, there are options to help others represent that ability if they have it - but they'll never be as good at it as the Warlord, because that is the archetype he represents.
I can see someone preferring that they handled it differently - but I can't really get someone saying this approach doesn't make sense, when it is simply the same natural approach of the class system that has been part of D&D from the start.