Although it's amusing to come up with creative ways to do the passive-aggressive thing, I don't think getting even ever works, especially when the person you're getting even with has no idea you're even annoyed in the first place. They don't seem good at figuring out folks might have a problem, or they don't care. The most grown-up thing to do would be to tell them that you don't like being preached at, but it's confrontation, even if it's gentle, and might spark a defensive reaction even if done very tactfully. Perhaps they'd be better off hearing it said by someone calm and caring before someone blows up at them.

Otherwise, I'd just let 'em take their turn. They're singing what they enjoy singing, not what they think folks will enjoy hearing. Maybe you could 'feed' them some nice trad gospel and ignore their agenda?

There ought to be some song somewhere that expresses what you want to say gently, without serving as a musical sledge hammer.

Here's a not-so-subtle reply to 'em: Dick Gaughan's 'Son of Man'.

Rick, I hear you, but these two women are on the dangly side of the lynching party.