A Defense of HufflepuffI think going from "I will take them all, regardless of their talents" to "all Hufflepuffs are inherently less gifted than the other houses" is quite the leap.
First of all, here's the English source material about Hufflepuff from the Sorting Hat, which is perhaps somewhat more canon:
Those patient Hufflepuffs are true
And unafraid of toil...
For Hufflepuff, hard workers were
Most worthy of admission...
Said Hufflepuff, "I'll teach the lot
And treat them just the same."
Good Hufflepuff, she took the rest
and taught them all she knew...
So it would seem there are themes of working hard and egalitarianism. Now, you may dismiss this as fluff, but I think these are pretty positive themes. I would guess that Hufflepuffs are more "well-balanced" than the other three houses, with personalities not dominated by a single attribute. Which again, you might say is just sweeping the dullards into one catch-all category. But working hard and keeping things in balance tends to lead to happiness and success in life. Which ought to be the primary purpose of a school, rather than a war academy or waspy evil wizard breeding ground. Everyone should have a chance to learn, and if you work hard, you'll succeed. In academic pursuits and life in general there is a lot to be said for diligence, 1% inspiration and 99% perspiration, that sort of thing. If you want to learn a musical instrument, you work hard at it. And then you get good at it.
And there is a fair degree of variance in intelligence/coolness/whatever for members of all the houses. Sure there are some duds but that's true of all the houses, and there are some bright stars too. Cedric Diggory was selected to champion the whole school in the Triwizard Tournament (although I guess it's not clear how much that selection process was rigged). There have been numerous Hufflepuff Ministers of Magic and Heads of Hogwarts. Surely they're not from the house of "don't tell the 11 year old he's slow". Meanwhile, Ravenclaw (for example) has had some recent doozies like Quirrel and Lockhart, who I think we can agree were both pretty lame.
And that's to say nothing of Hufflepuff herself, who was presumably a great wizard on par with the other three. She and Ravenclaw were besties, and there's no reason to think she was any less respected than the others, otherwise why would she have been included? Unfortunately there's not a whole lot about the personal lives of the Hogwarts founders on the wiki, but there's not much more about the others than there is about her. They all created a signature magical artifact and helped to bring the Sorting Hat to existence. Gryffindor was an accomplished duelist. Ravenclaw designed the sweet amorphous architecture of Hogwarts. Slytherin was an accomplished jerk and was really good at being a jerk. And Helga's contribution was apparently food charms for the feasts and such, she was kind of fat and good with food magic. But this matches her personality perfectly. Dueling is fine, obviously it's important to prepare people for the harsh realities of life. But shouldn't we be striving for a peaceful, prosperous, democratic society, with food and education for all?
Finally, I'd like to appeal to the literary angle. Harry Potter does not take place in the real world (obviously), there are wizards and shit primarily, but also a world of storytelling and moral absolutes. Sure in the real world, some people are demonstrably smarter or more successful than others, to the point that some people are classified as disabled. Maybe there are schools for the disabled in magical Britain, I'm not sure. But retardation is not a theme of Harry Potter. "Everyone is special" is. Ron is a podunk C student and Hermione is an upper middle class tryhard genius, but the books are very careful to remind you repeatedly that Ron has just as much to offer as Hermione for various reasons. And throughout the books concepts like goodness, kindness, and love are super duper important. To the point where they sometimes have actual, physical consequences in magical charms and such. So the fact that Hufflepuffs are good and honest and kind is quite relevant. They're part of the "good guys", and may even have access to powerful love magic or whatever that could be an overambitious Slytherin's undoing.
Mind you, I'm no Harry Potter expert, this is just one opinion. And if I had to say, all this anti-Hufflepuffism sounds like Slytherin talk to me