I think these threads are important because children rely on adults to protect them from abuse. And this was abusive. If we see these things happening to children and nobody ever says or does anything, then the parents think it is okay and the children keep right on suffering. If we say "well, I won't comment on this because I'm not a perfect parent either and perhaps those parents had a good reason for their behaviour" then it doesn't improve. Yes, we all make mistakes and have bad days - but we need to call each other on it when we are doing things that hurt children.
I know that this thread doesn't help the children in the original post. But notice how when one of the OP's family made a comment, the mother taking the video did move a bit so the son could see at least a little. Her comment didn't solve it, but it did have some effect.
And when I read these threads, my hope is that it gives us courage. Next time we see something like this, we'll feel supported by "our DISboard friends" in their agreement that these things are wrong. And maybe that will encourage us to speak up - not in a hostile way, but in a way that will help the parents and protect the children. Offer a suggestion, encourage the child, share your own experience (if you can mention being in a similar situation and how you dealt with it).
Research with abused children says that often it is those little supportive comments from other adults - often strangers - that kept them going and helped them to understand that what was being said and done to them was wrong and that it wasn't their fault.
That's my perspective, anyway.
Teresa