Why do teachers find it necessary to bring their own political views into the curriculum?

Who do they think they are? It's the same as teaching kids that only one religion is right. There is no difference. I get tired of hearing that these unqualified people who are suppose to be teaching specifics about history, science and math, are using it as a soap box for young impressionable minds to preach their own political agenda and viewpoints. Gag them and string them up. They get so used to being unchallenged in their everyday interaction with the kids, they maintain a supercillious attitude towards adults and think that they can write history by extolling their beliefs politically to kids in the clrooms. So many people scream about practicing religion in the clroom, so why aren't they screaming about teachers that spew out their liberal or conservative political beliefs. They are usually the liberal viewpoints that are being expounded. Let's hear it for a gag order on this!