For all of us who have always hoped to see a mainstream politician have the courage to unabashedly call for an end to marijuana prohibition, our days of waiting seem to be over. Last night on The Colbert Report, former New Mexico Gov. Gary Johnson – who is widely considered to be a likely candidate for the 2012 Republican presidential nomination — dedicated the entirety of his appearance to explaining why prohibition is a waste and new policies are needed. “I think that marijuana should be legalized,”…