It's really simple, just follow the steps :
1 : Sign in to your google account & go to youtube
(below is a image that proves, I have my google+ plus account linked to youtube)
2 : Go to http://www.youtube.com/account_advanced
3 : Click "Create custom URL"
4 : You will be redirected to http://www.youtube.com/account_username?action_custom_url=true, add some random text mixed with numbers in the textbox & click Create Channel URL
5 : Come back to http://www.youtube.com/account(You will be redirected)
6 : Click on "Return name to 'yourcustomURL', and disconnect Google+ profile" & you will be redirected http://www.youtube.com/account_revert
7 : Click OK button from the redirected page
8 : As what that redirected page sayed your Google+ profile will be disconnected from your Youtube channel
9 : Click save & that's all! you have successfully disconnected your Google+ profile from Youtube
I think unlinking your Google+ from Youtube makes no sense.
