[nebulosa]

I'd argue that the trend can come from two places, the less rational type you mentioned which appears to occur to enhance compatibility with an in-group, and the type which is based on having a set of base moral values which then affects our political beliefs. The latter of these can be seen as creating one layer of abstraction above the values, perhaps aiding in expressing those views, as well as enabling discussion with those who arrived on their views without consultation with their morals (due to copying others views, going with current trends in ideology, etc.).