Good protest songs are fun to sing.
Bad protest songs are not fun, and I see no reason to go on singing them, except to flatter the singer who wrote them.
I say this infrequently, hoping to avoid being considered a sorehead.
But I think that songs are not worth singing just because they express virtuous sentiments, or angry sentiments. Any more than bawdy songs are good just because they are bawdy.
An exception might be if the song had the potential actually to persuade people who disagreed. And I can think of at least one such song, "Tim Evans" by Ewan McColl. But these are very, very rare.