so. as I have read most of Grapes of Wrath at this point, I think I can shed some light on why the real Okies hated it. Basically, they are portrayed as idiots. Constantly being warned "don't go to california! there's no work! my whole family starved to death!" only to say such as "no, it can't be! we'll be fine!" Also such constant tidbits as "paw never did put much store by writin'. always made him feel uncomf'table."
Basically, Steinbeck's Okie is The Noble Savage. There are, I think, explicit comparisons made between the Okies and those they stole their land from.
It is making me enjoy my favorite book slightly less that... every character is just a horrible stereotype, except the preacher. Who, of course, is a misunderstood intellectual that the other characters constantly harass.
Also: the things these people get mad about confuse the hell out of me. They basically hate anyone who knows something, or thinks about something, or asks something, or expresses an emotion, or attempts to help them.
Kid: "well... I guess it was her time. Old folks got to die. I sure will miss 'er though."
pa: "WHY THE HELL YOU GOT TO TALK ALL THE GODDAMN TIME! YOU'VE EARNED A WHUPPIN, BOY! YOU'RE NO SON OF MINE, YOU DAMN FOOL!"
ma: "you're goddamn right. This boy never did learn his place."