"It's the ethos of Kumbaya that is being denigrated and not the sentiments expressed in the song, that is at the root of the remark about "A Kumbaya moment""

If by "ethos" you mean the naive notion that sitting around in a circle, holding hands and singing a really lame song was the same thing as doing something ...or even came anywhere near appropriately framing a grievance, then, yes, I agree with you.