A lot of people is just that, it's not a majority. You have seemingly mistranslated a vocal few in the US as the main cinemagoers over there, it's not. It's the run of the mill folk, the same run of the mill folk who believe Jesus is the answer to life. Only big cities have cinemas which will show NC-17 films, so middle US can only watch certain films.
The same run of the mill folk who will sit down and watch the Oscars. So if it's a taboo subject, it won't win unless it has major coverage at the time ie. Philadelphia = AIDS. If you look at the past ten years, only 'Crash' could be considered a subject which leads to debate but that's fairly relevant of the time.