I think you are probably correct as far as Twain being enculturated
against Indians.  We can see this in his characterizations such as Injun
Joe.  But the vehemence Twain displays in Chapter 19 of Roughing It
seems to go beyond how he was raised and is fed from something he has
seen.  

On Mon, 2014-05-19 at 23:26 +0000, Jerry Vorpahl wrote:
> I don't believe Mark Twain's opinion of the American Indian was formed by a=
>  couple attacks at stage stops. I grew up in Indian country, not so long ag=
> o, and heard the many derisive names and stories about them=C2=A0from quite=
>  substantial white citizens, including my mother. When I read Twain's comme=
> nts on the race, particularly "The Noble Red Man," they were not much diffe=
> rent than what I'd been hearing all my life. I believe the characterization=
> s have softened considerably in this era of Civil Rights, but at one time i=
> t was quite prevalent throughout the west.=20
> 
> ----- Original Message -----
> 
> From: "Scott Holmes" <[log in to unmask]>=20
> To: [log in to unmask]
> Sent: Monday, May 19, 2014 2:37:14 PM=20
> Subject: Mark Twain's cove on Lake Tahoe=20
> 
> I'm a bit surprised to not to see reaction on the recent decision to=20
> table any action for naming a cove on Lake Tahoe after Twain. =C2=A0My=20
> personal feeling is that the Washoe Indians have a much stronger claim=20
> and attaching Twain's name to Lake Tahoe would be a mistake. =C2=A0He didn'=
> t=20
> even like the name Tahoe. =C2=A0In every instance of his mentioning it he=
> =20
> would wax poetical about the beauty of the lake and turn poisonous about=20
> the people who lived there.=20
> 
> I recall asking sometime back if Twain ever recanted his hatred for the=20
> native American. =C2=A0I have not seen any instance of this. =C2=A0This is =
> quite=20
> interesting in light of his stands against racism directed at people of=20
> African ancestry and his anti-imperialism related to the Philippines.=20
> 
> It occurs to me that the timing of his travels through Shoshone country,=20
> during the later portion of the so-called Shoshone War may have much to=20
> do with it. =C2=A0He was stopping at stage coach stations every few hours=
> =20
> from St. Joseph to Virginia City, many of which had experienced attacks=20
> by Indians. =C2=A0He was completely unaware of the motivation(s) for these=
> =20
> attacks. =C2=A0He knew only that these strange people with inexplicable=20
> customs were attacking Americans.=20
> 
> Twain aspired to be gentry and the lives of the Shoshones, his=20
> "Goshoots", were just too foreign for him to comprehend. =C2=A0=20