I live in a Trump precinct in Maryland and if I said I supported Biden nobody would blink. If I went down to DC and said I voted for Trump people would look at me like I grew a second head.

I've never seen any evidence that it's "socially unacceptable" in any meaningful sense of the term to vote Democrat in a rural area. Where are you getting this?

It's just an extension of how rural vs urban societies handle people doing weird stuff they don't like.

If someone's doing something dumb and weird in a well off rural area nobody cares as long as they aren't actively negatively affecting people. Like maybe people will talk behind your back and think you're an idiot but that's about it.

If someone's doing something dumb and weird somewhere densely populated and wealthy people pour over the bylaws, call whoever they can to harass you and generally try to force you to stop by making your life miserable.

If someone's doing something dumb and weird somewhere poor, regardless of urban vs rural, nobody gives a crap because people have bigger problems.

Anecdote:

My son's soccer team from the city decided they wanted to make a statement against racism and kneel for the national anthem before games. At one of the suburban/rural schools, they were vehemently booed and yelled at by the parents and supporters of the other team.

(And the decision to kneel was made after a game the previous season against a different rural high school where my son's team mates were racially abused during the game.)

That’s not booing for voting, that’s about making a divisive political statement on a freaking kid soccer game. When you bring your activism into non-political contexts, don’t get surprised when people don’t like it.

So you’re saying it’s socially unacceptable?

In some contexts, yes. A kid's soccer game is a place to hang out together and have fun, not to relitigate the major point of social disagreement of the day. If some kids from some other school behaved in an improper manner, deal with this problem directly, instead of taking your grievance out on unrelated community whose only crime is also being rural, so surely must be bunch of evil racists.

They kneeled before every game. They weren’t singling out any specific community.

And the school pushed as hard as it could to have the original incidents addressed (the same school has been reported for other similar incidents previously) and the league did not impose any consequences.