Why Democrats shouldn't ignore their base

Democratic Party politicians seem to be forever distancing themselves from their own base. While a certain amount of centrism is necessary, I think the party has taken it too far. Chris Bowers on MyDD explains what the Democratic party loses by alienating its base:

However, leaving aside actual polling numbers for a moment, there are other reasons why catering to mythical, center-right swing voters and other 1990's chimeras should not always be the number one priority of the Democratic leadership. For one thing, swing voters don't contribute money, they don't volunteer for campaigns, they don't challenge right-wing media narratives, they don't keep Democrats active and energized to vote, and they don't expand the electoral playing field. Rather, these are tasks all carried out by the progressive activist base that Rothenberg thinks has "nowhere else to go" and which the Democratic Party "risks very little, at least at this point, in disappointing." The fact is that the resources and political machinery Democrats need in order to win elections are derived, in large part, from its progressive, activist base. Further, for all of the reasons mentioned above, which I outlined in more detail for an article for the Democratic Strategist), the rise of the progressive movement is the main reason that the Democratic Party has closed the resource and political machinery gap on Republicans since 2002. Thus, alienating that movement is extremely high-risk for Democrats, since participants in the progressive movement may not be swing voters, but they are certainly swing activists. Losing our support can be very dangerous.