This is very broad generalization. Also, it was meant to be a comment for discussion, not to be the exact reason why you got a 70.
In non-science courses where answers are not black and white as far as being correct or incorrect is concerned, whether you get excellent grades or average grades is far more dependent upon whether you've approached the subject lessons the same was as the teacher knows it.
If you want to adopt positions that contradict what the teacher understands the situation to be, you will be graded more sternly as you will be put to the test of convincing the teacher that his/her way is incorrect. Harder to do, if not impossible to do (depending upon the stubbornness of the teacher).
By "rubbing" the teacher the wrong way, I meant to say that what you wrote disagrees with the teacher at some level so your grade reflects that disagreement.