Two points might help explain (or spread!) the confusion.
1) SRI evaluations are primarily derived from a backward-looking description, whereas most people's ideas of "socially responsible companies" are forward-looking prescriptions. I hear people say, "a responsible utility gets electricity from wind, a responsible grocery sells organic, etc."
The opposite is the case for non-SRI! Financial evaluations are primarily about future projections, whereas most non-professionals definition of a "hot stock" is based off of its 12 month chart.
I'm not 100% sure what this means, except that popular conceptions of SRI sets it apart from traditional stock analysis.
2) SRI evaluations don't lend themselves to single variable continuous quantification. Unlike PE ratio or other financial factors, it is very difficult to produce a continuum of SRI scores. Intuitively, this would seem to make it more difficult to link SRI scores to stock valuation.