Dwarves - what is Tolkien's attitude?

[Kuruharan]

Then be of good cheer. He thought that they were the most fantabulously super-wonderful race in Arda!!!

Seriously now,

greedy, liable to curse jewels, working with the bad guys.

Unless you are referring to the material in the Lost Tales "The Nauglafring" I can't call to mind any story where the Dwarves willingly worked with "the bad guys." Unless you are referring to Mim, and his betrayal of Turin was not exactly of his own free will (although he certainly hated Beleg).

But Tolkien stresses that, as Dwarves, they are, after all, limited by their negative traits, not something they can help, poor things

So are we all. This was not something unique to Dwarves. The Elves were afflicted by perpetual snootyness (something Tolkien himself points out). Men were Men so what do you expect? Hobbits could be pretty naughty themselves (citation of basically the whole Sackville-Baggins clan [no offense to your namesake]).

The Dwarves, like everything else in the stories evolved over time. They did start out in the earliest conceptions as rather seedy characters, but the version of ancient dignity conveyed in the Lord of the Rings was (more or less) his final conception of them, and that is not particularly negative. I think he liked them okay.