How do you individually address an issue where the hiring manager is making a generic decision based on age unrelated to your individual performance (especially in hiring where they have no idea how many hours you personally work)?
Why should dying your hair and wearing skinny jeans affect your hire rate?
"-isms" don't work because they are rational individually, although they might work because they are stereotypically true. Or are you saying that the hiring manager should work on this individually... which would be actually just following the law.