i think he (the dad) was doing it not to test the uke, but to show the uke that he (the uke) was different then the step-mom. that what happened to the uke when he was a child would not happen to the little boy.
And no argument here about what you said concerning the kid. Because that's my point, there ARE better ways to handle it and it would be great if everyone could at least acknowledge that. And I also agree that it was a big fail on the seme's part the way he handled the situation with the uke. Even IF it was just to show the uke something. He was bringing up the uke's past trauma from his father leaving him behind so he could be with his new lover. And that holds especially true if he WAS using the situation to show the uke something.
exectly
not so much how he handled the kid (though i think that there are better ways to do it), but the way he tested the uke, hated that part, he was well aware of the uke´s trauma and he still did that scene...big fail as a dad/seme for me