Stupid is demonizing a candidate so thoroughly and so falsely that you will look like a hypocrite if said candidate were to win the nomination and carry our standard into the general.
Stupid is not realizing that all three of our leading Democratic candidates have strengths and weaknesses.
Stupid is canonizing one candidate with such passion that one would think said candidate was God Himself while at the same time pretending another candidate is the incarnation of Satan.
Stupid is leaving yourself with only three choices after such a demonization: 1) look like a hypocrite and vote for him or her anyway; 2) vote for the Republican nominee, a third party candidate, or an independent candidate (all of which have the same result of electing a Republican); and 3) not voting in the general at all.
Stupid is not realizing that the policy differences between the three leading Democratic candidates are smaller than they have been in generations, essentially meaning that, in the end, the potential presidencies of each will have same goals and policy priorities.
Stupid is allowing your devotion to one candidate, or your opposition to another, to get in the way of protecting the principles, policies, rights and priorities we all hold as Democrats.
Stupid is treating our friends as enemies.
Stupid is the Primary Wars.
Stupid is as Stupid does.