It's the (kcurie's?) doctrine of two definitions: the one you use to sell the package, and the one you use to talk about with people who know about what you talk about and don't need prodding.
Francois in Paris made a very similar point describing how the Republicans operate:
[Barak Obama] completely misses that the debate always happen at two levels, the general public and the base, and the terms are very different. The Republicans understand that very well and have played it for years with the outward message of "compassionate conservatism" or whatever to the general voters and the paranoid discourse to the base, "Christianity under attack" and all that crap.
Perhaps progressives are just too honest, or too idealistic in thinking that the progressive message should be understood by everyone, without diluting the language by catch phrases... Food for thought for someone who always thought that one type of language would be sufficient. Progressive Doublespeak seems needed.