Possible I suppose, although ignoring homeless beggers at freeway off ramps, driving past disabled cars with people in them, not knowing your neighbors, etc. would seem to go against that.
But hey, as speculation goes it's as good as any.
I'm not sure what any of that has to do with density as a factor in supporting liberal government policies. I don't generally drive the freeways as a necessity, the my relative experience passing all of those things is limited. As for knowing ones neighbors, that has little to do with whether they are downward spiraling or not.
As I mentioned above, liberal government policies in a densly packed environment can be completely explained as a conservative view of self-interest through the use of tax dollars to ensure a stable core of the social strata. What appears evidnent from that study is that what one believes to be in their self-interest does in fact change as population becomes denser, not that they become less self-interested. I'm not arguing that liberals are better people (which is what you seem to be falsely arguing against), I'm arguing what they believe is better for them is transformed through the experience of population density.