Ah...the trials of the evil basic college English class. It was my experience that you had to choose your section carefully - usually the teachers had some degree of leeway in selecting reading material and how papers had to be constructed.
Since I teach some required speech classes (the very evil, always troubling, nasty public speaking courses), I'm also required to make students write papers, and occasionally run into conflicts between what their English instructor likes and what I expect in my classroom. While I readily correct grammatical problems on papers (and count off some credit on repeated abuses), I don't believe in doing so to the point of negating or minimizing the ideas a student expresses.
It has been my experience that by the time someone is in college, critical thinking skills need to be developed, since they are going to need those in the real world. At the same time, I have a large number of students who aren't capable of distinguishing the difference between "there" and "their." How they managed to get through 12 years of education without learning that is beyond me.
One of the pedagogic problems in undergraduate school is often too much emphasis on teaching writing development as if every student aspires to graduate school, rather than trying to frame instruction toward more specific (and individual) career goals. I tend to be a big fan of andragogy, which encourages more self-directed learning and considers education a lifelong process rather than simply a jumping through the hoop experience.
Still, your instructor probably is limited somewhat by department requirements for that course, even if he/she has some leeway in how materials are selected. As it is in my own class, I have to require four short papers, one research paper, three speeches and at least four "engagements" in a sixteen week semester. I try to cushion students to some degree by granting more allowances for selecting individual paper topics that fit general guidelines. My students even choose whether they want an objective final exam or a take-home essay - I think that participation in the process hopefully encourages better performance.
But we get regular lectures from my department superiors about grade inflation, and I wouldn't be surprised if that doesn't happen in the English department at your school as well. Some instructors react to those concerns by creating ways to limit the number of students who can do well in the classroom. Obviously, that lesson becomes less about preparing students for success outside the classroom than adhering to an often vague concept of academic standards.