I don't think you have to literally "condone the sentiments" of a song, or adhere to a specific faction or cause related to in the music.

But there has to be SOMETHING in the song's lyrics that get you. Doesn't have to be a message or a moral. Could just be some detail, some turn of phrase, some unfathomable energy. If that's not there, why do you want to sing it?

There are two or three songs I learned ages ago simply because I liked the tune. And there's nothing wrong with that. But I never play them any more; I often forget that I know them. And that's cos ultimately, there's little in the lyrics that does anything for me.