I have an ES, but I'm certain the methods I would use to do the same would apply to you.
First, if you don't have a Youtube account, get one using your computer. Once signed in, set your security features to block adult content, or however Youtube chooses to call it. Next open your Youtube app on the TV, and sign in. The TV should give you a code to associate your Youtube account with your TV. Go back to your computer and enter the code in your Youtube account (it should direct where this is done). That should do it.
The only other way I can imagine, would be blocking content for the whole TV using the Security settings from the TV's menu, which will block all content.
Hope you find a fix that works for you.
I have recently purchased a Samsung TV model number UE40F6800SBXXU and I'm really pleased with the quality of the product. However, I don't seem to be able to keep inappropriate youtube content from the Social screen on the Smart Hub. I have two daughters aged 7 and 4 and I do not want them exposed to bad language. Many of the suggested videos have swear words in the titles with stars replacing letters and if my daughters access the youtube comments there are many full swear words on display. How can I stop these videos appearing on the social page?