I don't see it as trying to 'ram an agenda down their throats' - the class reads the book, they debate it and (with the teacher acting as the impartial mediator) each draw their own conclusions while having dissected the information contained within the story. This also takes in character development and tests the student's understanding of the motivation behind each character and any changes that occur as the story progresses. Debating the issues contained within a book using the characters experiences and views is, in my opinion, a good way to help a student look deeper into the text and understand not only who but also where and when they are reading about.
To remove books that may have a political slant also rules out a lot of the classics as many of them had an underlying social or political message, often disguised as satire. Just because this is easier to pick up on in books such as Huckleberry Finn and To Kill A Mockingbird doesn't mean that it isn't present in other books as well or that it shouldn't be acknowledged and discussed. Are we to block all books that have an overt or covert commentary relating to issues of the times that they were written or set in? If we do then reading lists will shrink to such a narrow margin of approved texts that we'd be doing a disservice to the students studying them. And again, the use of an underlying message within a book and the motivation of the author in writing it is also a valuable discussion point for students, as well as showing them that a book can be so much more than merely a selection of words strung together in an entertaining fashion. It can be a tool to reach people, to share a message and express both love and dissatisfaction for the times the author found themselves living in.
But maybe my opinion on this should be discounted as in spite of my own love of literature that I developed thanks to my own mother at a very early age my dried up raisin of a womb has failed to provide me with children who will be entering the educational system, making my viewpoint null and void.