Well, Hemmingway considered himself a writer, and at the time was probably thinking of Twain as a newspaper columnist. (Bob Roach's Plan For Circumventing A Democrat) Columnist/communist- they kinda sound alike, I guess, but he also tried his hand as a publisher. So right there are two occupations which might get him on the shit-list of some literary-minded guys.
The man was a genius with words...countrified Americana. Perhaps the very essence of who we are as a people. Or, were.