The poem reads something like
At the well-side
The cherry-blossoms are dangerous
Drunk on sake
As you can see, by itself its not a fascinating or lovely poem, but I think what resonated with the priest was the fact that it was written by a young girl (13 years old), and that its a fairly catchy slogan for the dangers of booze. And maybe the juxtaposition of cherry-blossoms with danger has an unusual quality to it.