As the more rational people continue to point out; the three leading democratic contenders are the strongest candidates, and very little separates their policies. Since all of that is a wash; as much as you hate to admit it, if you're voting democrat, you're voting for style.
This is odd because our understanding of politics (especially in the light of the recent years of political failures) is that it is a SERIOUS THING.
With the parity of our leading candidates however, we're forced to focus on their minute differences and details; you know the superficial stuff. This is why we have intra-party political discussions that are eerily reminiscent of jr. high (also known as middle school in other places). Not surprisingly we get into extreme confrontations with our contemporaries (democrat/progressive/liberal/whatever you call it nowadays). So now we have a democratic voting bloc fractured into cliques, who wander the halls (of the internet and elsewhere) in bristling packs of insularity.
Why? Because nothing is worse than a heretic. Those people who almost agree with you. The alien mindset (in this case Republican) is written off as obviously wrong, an abstract evil to be confronted at a later date. Your fellows (in this case Democratic voters) are subject to acute, harsh, and intense criticism. Perhaps it arises from the staggering amount of commonalities that leave you frustrated that the others "get" so much of it and just happen to be "misguided" over that last bit of difference.
You can convince some of those people of the correctness of your understanding and you should, it's good politics; but hoping, wishing and working towards full unanimity in the party isn't democratic, it's fascist.