Yeah rhetorical flexibility is probably an important ingredient for an effective social order (not necessarily a moral one) but you have to consider what it takes to embrace an idea. My sense is that ideologies usually emerge bottom up from individual values - anything top down runs the risk of being misaligned, and therefore incompatible and won't be accepted. Further, if its too inconsistent or incorrect then its vulnerable to opposition and is no longer "the least bad choice in the room."
It seems that these populist ideologies are built on the shared values of chauvinism, revanchism, and various maladaptive psychological copings to the usual problems and hardships of (modern) life.
And it seems that the ends of the spectrum exhibit different manifestations, as in the current "left" uses ideology for purity testing and the "right" uses it for loyalty testing. (I wanted to link to some details on this, but I can't find it now. :/)