Right, because ideological purity is much better than pragmatism. You have no preference at all between the candidates, because none of them favour complete legalisation? You'd rather have no decriminalisation than just some?
The drug war is only one of many reasons that I am apolitical. I don't accept that I have a legitimate choice -- to me, voting would be tacit acceptance of the legitimacy of our political process.
Sanders filed a bill to remove cannabis from the controlled substances act altogether, which would defer any decision on its prohibition or legal status to individual states: https://www.govtrack.us/congress/bills/114/s2237/text. It's not full all-at-once nationwide legalization, but it's not a mere decrease in federal penalties either.