The actual values at any given time are not really that important, though - it floats around a center (which is much more liberal today than it was 50 or 100 years ago) but the range is still there.
But the center is still culturally different. To have liberal views in the United States and liberal views in Canada are two VERY different things - nevermind countries where fundamentalist religion plays an even larger role in ideological definition.
Thus, the tie-in to political ideology is absolutely irrelevant to the study; the gene seems to increase novelty-seeking. That's it. In some cultures, that may or may not correlate to political ideology, but political ideology itself does not correlate back to genes.
That's just a more nuanced (and, yes, accurate) way of saying what I says.
I've seen a fair range of data on the heritability of personality stuff, which is complicated by the fact that the actual measurement of personality is still sort of in flux. But what I think is a more important confound than gene-environment interactions shaping personality is the causal kid of that interaction - the back-and-forth between the personality traits and the social environment that the subject ends up in. There's all sorts of confounds that could arise there, from the family level right up on to the societal.
Your earlier statement implied a loose cause-effect relationship between disposition and ideology, which I would argue there is virtually no evidence for. This recent paragraph fixes that, and it much better in line with the science (that I'm aware of).
More and more evidence of a synergistic gene-environment effect is becoming available in behavioural genetics, which is part of what I think you're alluding to. The idea that genetics and environment interact to produce an effect, which is turn produces a feedback loop (positive or negative) back onto gene expression is a relatively new one in the behavioural sciences, but it appears to have significant merit.
That also may be occurring here. The fact that this is a dopamine receptor is particularly telling, considering dopamine's involvement in the reward pathways of the brain. The produced behaviour made more likely by the genes and their subsequent environmental interaction is likely being reinforced by the way the behaviour actually alters gene expression itself (I would hazard an education guess that dopamine expression increases resulting in an increased presence of it in the synapse following positive behavioural outcomes).
Regardless, the action of this receptor allele and its subsequent behavioural effects have very little to do with political ideology and more more to do with the resultant personality and social competence of the person in question. The fact that those layered psychological traits happen to correlate to a particular fuzzily-defined political ideology in this time context is virtually irrelevant because that ideology is socially defined and non-rigid. It's a stupid trick to gain media attention, and does nothing but promote the lunacy that there is a significant discrepancy between people who identify as 'liberal' and people who identify as 'conservative.'