To respond to your comment about not wasting space on your SOP for low grades, I absolutely agree. But there is nothing stopping you from writing an Addendum that can go right after the body of your SOP. I was told by all the grad students in the lab I worked for that an SOP should highlight only the positives about your past, the reasons/inspirations you're choosing to go to grad school and what your goals are for the future. The addendum can briefly explain why you received low grades and what you did to improve and how you improved (e.g. does your transcript show an upward trend?).
yeah it sucks but at real schools they hire professors for research and not teaching ability (although i'd love to hang out with your dope liberal arts faculty some day)