Yes there is, if said stress relievers are sentient. I'm all for ultra-violent justice or violence for the sake of research or production. But this is just asshole-ish, in my opinion
And no argument is actually made. Considering that one of the plot points is that stressed out yukkuri = dead yukkuri, it makes the parents even more assholes because the trauma is causing more damage.
The parents have no knowledge that there kid can see them. The anon doesn't even know how the image is continuing changing. So basically we are the only ones with full disclosure.
You're right that the parents don't know the children can see them. It's what shows that they're trash. If they really loved their children they wouldn't say such things at all.
Unfortunately your other point is a straw-man. Even if he doesn't know how exactly it works the results can still be seen.
I think we all need to relax here. Why does it matter if they are assholes or not? It doesn't really add anymore to the story if they are assholes or saints. They're being yukkuri, and that's that.