I agree with you on Kaiser needing privacy and I'm also doubtful of Nathan's motives. At the same time, it seems to me that Child Services is asleep at the job here. Those bruises are not from a slip n slide, they are switch marks. David is violent and there is video of him and Jenelle threatening Kaiser on video, and poor Kaiser's terrified reaction. I fear for Kaiser because he's Nathan's twin and I can see David picturing getting even with Nathan through little Kai.Now, Nathan is not a model citizen either, so give custody to Doris. Jenelle can still see Kaiser, but not with UBT present. If Child Services isn't doing anything to keep Kaiser safe, I can see Nathan deciding to publish the photos in order to push them into taking some action. As dumb as Nathan is himself, I think even he can see the writing on the wall that his son os at risk for being either seriously injured or killed at the hands of David.
Also have to say that I'm very disappointed in Babs. She is kissing Jenelle's ass at the expense of Kaiser's safety. I get that's her daughter, but she's also a sociopath and she's made her own bad choices, the only important ones are the Jace, Kai and Endtable who have no choice in being born to such a shit "mother". I can see David killing Kaiser and Jenelle helping cover it up, all while crying about how David is such a good man.