One can word it based on the behaviors alone: "I don't like it when people do X and Y" versus "I don't like it when Mormons do X and Y" versus "Mormons are bad because they do X and Y". Why single out Mormons when others may do the same? The first can communicate pretty much the same as #2 and #3 without potentially offending groups. I don't think the first two should be banned, but #3 is stretching it. If I ran a discussion forum, I'd consider banning #3, perhaps first with a warning and a how-to on rewording.
If somebody believed "Hollywood is possessed by Satan", saying so wouldn't do any good. It's not objective and doesn't carry useable information. If you instead focus on specific behaviors, such as having too much violence & sex in movies, then a fruitful discussion can form without demonizing specific groups. If Mother Theresa produces movies with sex & violence, she should be held to the same criticism and standards, which should be based on observable actions/results.
Anyone criticizing should first establish the observable things (violence, oppression, whatever bias or other behavior) and then state the argument for how that is widespread in a culture, region, country, group.
To address your examples, #1 is okay as it doesn't make any associations with a culture (at least if we assume X and Y are void of such), #2 is for me the most problematic, as #3 is directly claims that a culture/group/region has a problem, because X and/or Y, whereas #2 is just singling out a culture for no apparent reason.
Interestingly, I think the majority of citizens would disagree with the ruling. (And it was partly overturned a few decades later.)
Furthermore, the ability to state facts and opinions is important. If someone finds a culture oppressive he/she ought to be able to say it so.