I'm pretty sure all we intolerant jerks have an amazing amount of understanding for people who forget words. Why, we've been known to do it ourselves.

Even a "cheat sheet" is not the end of the world. RUS is also not the end of the world--but, as they say, you can see it from there.

Your choice--if you want to separate serious singers from people who want a folk "hymn sing", that's what's happening.