[camjohnson26]

Their lower class applicants had country music listed as an interest on the resume while higher class had classical music.

Classical music is objectively more intricate and difficult to master so I’d expect it to signal a more qualified applicant if they’re using music as a representative interest of their personality.

[throwawaymath]

Are you being facetious? I don't think the candidate's favorite music genre is being explicitly used as a job qualification. They're not filtering on it because it's relevant to the job.

[camjohnson26]

Why would you put musical interests on your resume if you didn’t want it to be used as a filter? As a resume screener I’m going to assume anything in the resume is fair game, and there’s objective reasons to select a candidate who’s self aware enough to know that country music isn’t sending a good signal.

The fact that they like country music isn’t the problem, it’s that they thought it was a good interest to put on a resume.

[throwawaymath]

Please tell me a few of these objective reasons why someone who puts "country music" on their resume as an interest isn't sending a good signal.

As a resume screener you should calibrate your recruiting process to be empirical. What you're describing doesn't sound empirical at all.