I beleive there is more to it then seen on the surface. Tolkien's loyalty lies with Rohan, but he is honest (one of his great points, too) enough to let some dubious things slip.
And, though Dunlandings are
deceived by Saruman to believe that Rohirrim are cruel - i.e. not much direct dealings between two peoples, the grudge lies deeper - it is admitted that dunlendings are original inhabitants.
Yes, I believe I can sympathize with them, sure
