> What is democracy then? On what reasons are people allowed to base their vote on?

Who is doing a good job. Non-sectarian ideological preferences. Policies. Who they want to have a beer with.

> I don’t think it's possible to cleanse your brain of every iota of cultural, ethnic, or religious background and just vote as "yourself." Your preferences are melded, in part, by your group identity.

No, but you can demand assimilation to where traces of group identity become secondary to non-sectarian factors. Catholics and Protestants in the U.S. used to be deeply divided politically and now that’s not much of a predictor.

> And you think decades ago before your suburb was "corrupted" by anti-assimilation, that people's group identity didn't predict how they voted

In my suburb growing up everyone was highly assimilated and any group identity had become extremely shallow. Our group of neighborhood kids was one person with a Russian surname, two pairs of siblings with Anglo surnames, and then me with my Bangladeshi surname. Not once the entire time growing up did we perceive ourselves as having a different group identity from each other.