Leni
The correct term is socialist.
I agree that the word progressive is innappropriate, if you are to look at the outcomes of the Progressive movement. In its extremes, there have been horrible attrocities due to liquidation of parts of nations populations, due to far Left leadership.
What is useful about the term "Progressive" is that it describes a broad range of related movements. No one is saying Social Democrats will bring about the same government as Communists, but they have the same philosophical basis.
According to Bill Clinton, 75% of Iranians are "progressive." While Clinton and Iranians live different lifestyles, both tend towards heavy centralization of government, as much as they can achieve. The mullahs of Iran, obviously, being more successful at it than Democrats in America.
Another example has to do with campus speach. Back in the hippie age, there was the Filthy Speach movement on some campuses. Imagine carrying around a sign with the word "Fuck" on it, in what was a more polite society back then? Some of these same people are not responsible for coming up with campus speach codes which act to inhibit certain things from being said (and therefore, supposedly, from being thought). Being repremanded for "innapropriate laughter"? While the strategies of the movement change (radically open and free speach, to regulated speach, in the course of a few decades), the people, and more importantly, the goals remain the same. "Progressive" accurately refers to both the radical free speach advocate and the authortarian who wants to limit it.