"When it comes to aesthetic uses, sentimentality is usually a clear sign of a reactionary posture."
[B:] I'm almost tempted to agree 100%. At the risk of invoking Godwin's Law, the Nazis (who i guess we can never reference anymore on mailing lists since Godwin's law came up?) were based almost entirely on sentimentality and high-flown, sweeping romantic ideas that harkened back to a golden age -- a golden age entirely incongruent with facts, but nonetheless.
Having said that, there's a lot of sentimentality on the left for, example, the "good ol' days" of the IWW's classic run (which actually looked like a living hell), the Civil Rights Movement, and more. And there's something about listening to the labor folk songs of folks like Joe Hill, Woody Guthrie, and the like, that can bring an inspirational and/or sentimental kind of tear to the eye. But those songs are usually always forward-thinking ballads, not ruminations on an idyllic past that we need to get back to.
-B.