Roger Olsen is spot on on this one-- and let me add that what it now means to be a theological conservative today is far from clear. I am not sure that many of them are conserving much of anything significant. And substituting the word progressive for liberal doesn't fix the problem either. One has to think extremely highly of one's intelligence and vision to label their views as progressive. It's like all those 18th century elistists referring to their time as one of Enlightenment. By the way, I'd like to see Olsen's thinking applied to the modern political spectrum as well.
No matter how hard they tried, historical theologians analyzing nineteenth century theology (and "nineteenth century theology" only ends at 1914 or 1917) could not break the spell of trying to put every Christian theologian somewhere on a spectrum of right to left or left to right with modernity being the criterion of placement. So, by this common analysis, which still works its magic over us, Hodge and theologians like him belong toward the "right" end of the spectrum, Schleiermacher and Ritschl and their followers belong toward the "left" end of the spectrum and the mediating theologians are arrayed at various points along the middle. The often unspoken question the answer to which determines where a theologian belongs on the spectrum is to what extent he or she accommodated to modernity.
Also, where does Kierkegaard belong on that spectrum? The usual way to deal with the Danish theologian is to treat him a philosopher, but anyone who reads him knows he was a theologian. He had a degree in theology, at times wanted to teach theology (but you had to have the King’s endorsement to have a teaching position in the university and Kierkegaard's enemies blocked it), and most of his writing deals with Christianity either directly or indirectly. Although he was reacting against Hegel and his followers, he was not accommodating to or reacting against modernity per se. He certainly wasn't "liberal" in any usual sense of that word. So, to rescue the spectrum, people like Kierkegaard are usually excused by being relegating to the separate category of philosophy.
I suggest the reason for the obsession with the spectrum is the ease it offers to categorizing nineteenth century theologians. The emergence of the phenomenon of mediating theology reinforced its apparent appropriateness. But I also suggest it never really worked without serious distortions. People have held onto it simply because it's easy. And it has become a useful polemical tool for labeling and dismissing theologians. Almost everyone wants to see himself or herself as somewhere in the middle of the spectrum, so the spectrum itself becomes relative to the individual using it.
I say let it die. Except when talking about theologians who really do fit on it by their own admissions—as pro-modern or anti-modern or attempting some kind of synthesis.
The traditional "right to left, left to right" spectrum for categorizing theologians and theologies was problematic from the start. It began as a way of categorizing nineteenth century theologians and it was tied to modernity. Theologians were placed on it according to the placer's judgment about the theologians’ accommodations to or rejections of modernity. That spectrum didn't ever work well, but it became especially problematic in the twentieth century as many theologians no longer responded to modernity.