If they wanted to cut out an entire sideplot or scenes whose absence from the film would not render the rest of the movie senseless then it is totally alright. Again, the Cinema Paradiso analogy holds, where almost a half hour's worth of the film was cut out because it focused on a secondary plotline(the romance) and made THAT plotline the crux of the film instead of the primary plotline(the relationship between the protagonist and the projectionist). Majority of the people I know who have seen both versions of the film far prefer the edited version because it is more seamless and focused than the uncut version. Heck, the uncut version was a box office disappointment when it was first released, and then when they released the edited version in theaters, that was a huge hit.
If the studio thought those 20 mins of Snowpiercer unnecessarily complicated the story and characters and/or dragged the film down, and/or took away from the main point of the film, then they are well within their rights to have those scenes removed for smoother and crisper storytelling. Don't know how accurate that "film should be understood by audiences in Iowa.. and Oklahoma" quote is. Seems splintered and slightly out of context to me. Could just be a classic case of online blogs making a mountain out of a molehill.