Ms. Cornelius has an excellent post about teacher biases entering the classroom. While I don't agree with her 100% on this case, I'm sure we're above 80% here. I clarified my position in a comment to her post.
When we discuss current events and the like in my class, I give students my opinion--and they know it's mine. They know I'm not sugar-coating it for their delicate ears. They also don't have to worry about their grade dropping if they don't share my opinion (I teach math)--I'm not so sure they're as safe in an English or social science class.