I HAVE BEEN SUMMONED BY THE ALMIGHTY ZOOKEEPER!
'Sup, Zoo? Long time, no see. Hope I'm not necro-ing this, but the comment you linked is actually one I've been looking for to use as reference for some time! Thank you very much!
Now, time to get to something I like to call the "Soul Absorbing Bone Tower" effect! From back in the days when I played Yu-Gi-Oh! Oh, Middle School, how I TOTALLY DO NOT miss you.
Anywho, there were months of debate over cards that said "If there is another X present, you may not attack this" or "If there is another X present, you may not attack any creature other than [Card Name]."
This loop creates situations where you either can't attack because you have to attack a creature and none of the creatures are attackable OR you can not attack anything BUT a thing that can't be attacked.
In the latter situation, it was ruled (house and then official) that you can attack either of the things that say you can only attack them, but the former and more applicable here was ruled three different ways. First, house rules said that no, you cannot attack. Then we decided that was stupid and cheesy and someone eventually ruled that it allowed you to attack as if there were no creatures, because all of them were treated as untargetable leaving the player the only target.
The final, and I think official ruling was that they cancel eachother out, and that's what it looks like Stealthy does here.
Toodles! See you all in a month or two when I get bored again! Stay classy!