People are slack jawed dumbasses for using a word colloquially? Thing is, the word ironic I think works a lot better, and gets the meaning across much better than any other word I can think of for the purposes of the song. It's not the "wrong goddamn word", it's the right word used in a technically inaccurate way. If the song were trying to teach the english language, or if it were actually about irony (it's about life, isn't it?) you would have a point. Songs have absolutely no obligation to do so, however, and I would hope most artists understand this point.
How....how in the world does that make them lose all credibility? That doesn't make any sense whatsoever. You really would discount someone's opinion just because they don't nitpick over the grammatical correctness of everything they say? Your argument is losing credibility here, I think, and exaggerating doesn't help.