It's OK to say you dislike a movie because it was bad. It's when you say that you dislike a movie because its ideas are problematic that people get annoyed.
This became especially apparent to me when discussing The Blind Side with a friend. When I brought up the racially problematic elements in the movie's selective portrayal of a true story, she resisted my analysis, arguing that it was just "a beautiful story."
I'll admit that she could be right. Maybe I'm looking too much into things, but there's still something to be said for looking at all.
When discussing films, we have to remember that they aren't just delivered by a stork, ready-made. The decisions made by filmmakers are conscious and intentional. If something in a movie is problematic, there's a good chance that someone had a chance to fix it - and chose not to.
Take for example the twin Autobots in Transformers: Revenge of the Fallen. In spite of the blatant similarities to offensive minstrel characters, Director Michael Bay defended them, saying they were just comic relief.
Nothing is just comic relief, and no movie is just a movie. Every film you see is functioning with an agenda on some level. It could be something as simple as eliciting sympathy, or it could be a strong political message.
It's essential to identify when a film is saying something problematic, because in our society of lying politicians and false advertising, looking critically at the world around us - especially the media - prevents us from being unknowingly subverted.
That's not to say that films with agendas are inherently bad. On the contrary, films like Blood Diamond and Supersize Me tap into the communicative power of movies to try to bring about positive social change.
I also don't mean that problematic movies can't be likable. I still enjoy Scott Pilgrim vs. The World even though certain aspects of it could be viewed as uncomfortably heteronormative, and The Last Samurai is still one of my favorite movies in spite of its white-man-out-natives-the-natives undertones.
Even if your ultimate decision is to enjoy a movie anyway, it's important to recognize choices on the filmmaker's part that could be construed in a negative or insensitive way.
Viewing films in a critical light makes you more conscious of the world around you. Before you get defensive, take time to consider why filmmakers with agendas might not want you to take a closer look.