While i clearly don't aprove forcing you to do this, i'm glad you saw why people in general hate them, you witnessed the true nature behind their so called "cutesy and fake easiness", now you know your prey, anything that remotely act like this one should be purged, anything that is truly nice, i'll leave it to your judgement and preference.
And now the boy snapped! He is starting to discover the joys of abyuse! Ahhh, puberty. Good times those were... Except that there were no Yukkuri to abyuse.
It doesn't matter, they invaded a human place, and as their initial attitude showed, they weren't going to accept this place didn't belong to them and leave. Even if this story wasn't about some stupid and destined to fail plan to make school kids drop bullying and have them focus that on abyusing yu's, this yukkuris would had called their own doom with any other group of humans for invading their places and then acting up when called on it.