Should we always support Democrats because the Republicans are so much worse, or should we focus on using our influence to guide Democrats in the right direction? These ideas are in constant tension on this blog, and opinions vary widely. Note that the latter requires substantive discussion of ideology and policy while the former is merely about partisanship. Occasionally I see people here say, "Why are we wasting our time attacking Democrats when we ought to be attacking Republicans?" The proper response is, "if we don't advocate for change within the party, who will?" The Democratic establishment has a great deal of room for improvement.
Kos is wrong when he places partisanship above all other concerns--what we really want is to get the best possible policies actually implemented. (For this reason, I think the front page should delve a little deeper into ideology. Jerome a Paris recently made a good argument about this: http://www.dailykos.com/... )
How can we best use the influence of the Dailykos community to get the best policies implemented? I would argue that our most important role is in fact to improve the Democratic party from within. While we can play an important role in defeating Republicans, our most significant contribution will come from changing the Democratic party itself.
In order to change the Democratic party, we need to show the establishment that we cannot be taken for granted. Democrats need to earn our active support. Considering how hideous the Republicans are, it's true that we may be expected to vote Democratic except in very unusual circumstances. However, active support from this community can come in many forms. Democrats who support bad policies should expect to lose our financial support and our enthusiasm. Just because a mediocre Democrat is better than the Republican doesn't mean we're going to open our pocketbooks and volunteer to help their campaigns. Democratic politicians and candidates need to be conditioned to pay attention to us and support what we support (think of it like dog training--the dog gets rewarded only when it does something we like). In some cases we should be getting involved in primary challenges--if we can strike some of the same kind of fear into our Democratic politicians that the Republican base strikes into so many of their politicians, we will be successful.
Discussion of ideology here is important and can influence the broader community in the long run--I believe that our influence in this is more important than all of the fundraising and political horseracing that this community is also so good at. I think we can also influence the ideology and actions of Democratic politicians if we teach them that we will support them and reward them (significantly) only if they support us. Attacking some Democrats for boneheaded actions is productive and can strengthen our position vs. Republicans.