Teachers of any kind have a grave responsibility and a sense of authority. The are passing out information to these children's (sometime unquestioning) minds. The above article is a interesting article. It of course it highlights known problems in some school systems. The sad part is that this debate even has to be had. I fortunately had a very technical major, where there are easy methods of evaluating methods of doing something. I realize there are other majors where instead of actually grading with well defined criteria, you will be graded by only one person's opinion. I believe that college professors are for the most part professional enough to put their biases out of giving grades, but every profession has it's bad apples. I guess this is where the article is coming from.
I don't know if we need laws supporting ideological diversity among college professors, but I would support laws against discrimination for many reasons at the public schools (now you can be discriminated against for almost any reason under the sun, but that is another separate problem). Of course private schools are allowed to do what ever they want, and discriminate against people with different view points (although not different race). A devil worshipper school should not be forced to accept a Christian as a student, and a gay and lesbian school should not be forced to accept straight students. Additionally, private schools should be able to hire and fire their factually for valid ideological reasons, such as a Christian school firing a teacher for having children out of wedlock. Although, I do support a school if they want to be just a boys or just a girls school.
But just to highlight the problem that some teachers have of keeping their opinion (which are not facts), to their selves here is a story.
When I returned to California, I appeared on the Michael Reagan radio show to talk about my experiences. Before I could begin, Reagan had an anecdote of his own. His daughter was a freshman in college and had just begun her classes. One of the first courses the granddaughter of Ronald Reagan elected to take was a beginning acting class. On the first day, in the course of introducing himself the professor told the students: "I am a liberal Democrat. If there are any Republicans here, I advise you to drop the class."
That teacher was teaching acting. Which you can make the case that all politicians are actors, but not the case all actors are politicians.