Why do Democrats want high taxation as their brand?

Ezra Klein's piece this morning is headlined: "Democrats will lose now. But they can win later." The next thing you see is a chart depicting "Tax increases over 10 years if Congress passes..." various proposals (or nothing).  He begins:

Democrats are going to lose this one. The first stage of the emerging deal doesn’t include revenue, doesn’t include stimulus, and lets Republicans pocket a trillion dollars or more in cuts without offering anything to Democrats in return.

Pocket? There's nothing to pocket! All we're getting is a trillion less in overspending. The debt piles up at an alarming rate all the time. Holding back one trillion over the next 10 years isn't much (seen in proportion to the vast spending).

But, in the mind of Ezra, that nonexistent money goes to Republicans, and Democrats deserve something in return: taxing and spending. (Otherwise known as: revenue and stimulus.) That's the Democratic Party brand — as spun by Ezra Klein.

Why is that a desirable brand going into the next election? I would think the Democrats would want to own some of the spending cuts, to pose as reasonably frugal, mature, and realistic. Why cede all that to the Republicans? I understand the preference for taxing over cutting spending, but this giddy enthusiasm? Shouldn't you hide that?